This document describes a survey to discover asteroids interior to Earth's and Venus' orbits using the Dark Energy Camera on the Blanco 4m telescope in Chile. The survey has discovered three new asteroids so far, including two rare Atira asteroids completely interior to Earth and one Apollo asteroid crossing Earth's orbit. Two discoveries are estimated to be over 1 km in diameter. The survey has covered 624 square degrees near and interior to Venus' orbit, detecting about 15% of all known Atira asteroids. The survey aims to better understand asteroid populations in the inner solar system to improve models of near-Earth object populations and impact risks.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Neowise observations of near earth objects- preliminary resultsSérgio Sacani
The NEOWISE survey observed near-Earth objects at infrared wavelengths, detecting over 130 new NEOs. Analysis of the 428 NEOs detected allows estimates of the total NEO population between 100m and 1km in size. The survey found an estimated 981±19 NEOs larger than 1km have been detected, meeting the Spaceguard goal of detecting 90% of objects this size. It also estimates 20,500±3000 NEOs larger than 100m. The cumulative size distribution is best represented by a broken power law.
This presentation provides an overview of NASA's Science Mission Directorate that carries out the agency's missions for Earth science, heliophysics, astrophysics, and planetary sciences.
http://science.nasa.gov/
XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Proto...Sérgio Sacani
This document presents the first results from the JWST XUE program, which observed 15 protoplanetary disks in the NGC 6357 star-forming region using MIRI. For the disk XUE 1, located near massive stars, the following was found:
1) Abundant water, CO, CO2, HCN, and C2H2 were detected in the inner few AU, indicating an oxygen-dominated gas-phase chemistry similar to isolated disks.
2) Small crystalline silicate dust is present at the disk surface.
3) The column densities and chemistry are surprisingly similar to isolated disks despite the extreme radiation environment, implying inner disks can retain conditions conducive to rocky planet
The Search for Distant Objects in the Solar System Using Spacewatch - Astrono...Eric Roe
This document describes a survey conducted by the Spacewatch Project to search for distant and slow-moving bright objects in the outer solar system beyond Neptune. The survey used data taken over 34 months with multiple night detections to achieve sensitivity to motions as slow as 0.012 arcsec/hr. This allowed the survey to be sensitive to Mars-sized objects out to 300 AU and Jupiter-sized planets out to 1200 AU. No large objects were found at low inclinations despite having sufficient sensitivity, allowing the authors to rule out more than one or two Pluto-sized objects to 100 AU and one or two Mars-sized objects to 200 AU for low inclinations.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Neowise observations of near earth objects- preliminary resultsSérgio Sacani
The NEOWISE survey observed near-Earth objects at infrared wavelengths, detecting over 130 new NEOs. Analysis of the 428 NEOs detected allows estimates of the total NEO population between 100m and 1km in size. The survey found an estimated 981±19 NEOs larger than 1km have been detected, meeting the Spaceguard goal of detecting 90% of objects this size. It also estimates 20,500±3000 NEOs larger than 100m. The cumulative size distribution is best represented by a broken power law.
This presentation provides an overview of NASA's Science Mission Directorate that carries out the agency's missions for Earth science, heliophysics, astrophysics, and planetary sciences.
http://science.nasa.gov/
XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Proto...Sérgio Sacani
This document presents the first results from the JWST XUE program, which observed 15 protoplanetary disks in the NGC 6357 star-forming region using MIRI. For the disk XUE 1, located near massive stars, the following was found:
1) Abundant water, CO, CO2, HCN, and C2H2 were detected in the inner few AU, indicating an oxygen-dominated gas-phase chemistry similar to isolated disks.
2) Small crystalline silicate dust is present at the disk surface.
3) The column densities and chemistry are surprisingly similar to isolated disks despite the extreme radiation environment, implying inner disks can retain conditions conducive to rocky planet
The Search for Distant Objects in the Solar System Using Spacewatch - Astrono...Eric Roe
This document describes a survey conducted by the Spacewatch Project to search for distant and slow-moving bright objects in the outer solar system beyond Neptune. The survey used data taken over 34 months with multiple night detections to achieve sensitivity to motions as slow as 0.012 arcsec/hr. This allowed the survey to be sensitive to Mars-sized objects out to 300 AU and Jupiter-sized planets out to 1200 AU. No large objects were found at low inclinations despite having sufficient sensitivity, allowing the authors to rule out more than one or two Pluto-sized objects to 100 AU and one or two Mars-sized objects to 200 AU for low inclinations.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
This document summarizes the discovery of a transiting circumbinary planet (PH1) in a quadruple star system by volunteers with the Planet Hunters citizen science project. PH1 orbits outside a 20-day eclipsing binary consisting of an F dwarf and an M dwarf star. It has a radius of 6.18 ± 0.17 R⊕ and an upper mass limit of 169 M⊕. Beyond PH1's orbit is a distant visual binary bound to the system, making this the first known case of a transiting planet in a quadruple star configuration. Planet Hunters volunteers identified transit features in the Kepler light curve of KIC 4862625 through visual inspection and discussion, leading to the confirmation and characterization
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
This summarizes a scientific study on long-distance quantum teleportation between two laboratories separated by 55 meters but connected by 2 kilometers of fiber optic cable. The key points are:
1) Researchers teleported quantum states (qubits) carried by photons at 1.3 micrometer wavelengths onto photons at 1.55 micrometer wavelengths between the two laboratories.
2) The qubits were encoded in time-bin superpositions and entanglement rather than polarization to make them more robust against decoherence in optical fibers.
3) A partial Bell state measurement was performed using linear optics at the receiving end to probabilistically teleport the quantum states over the long distance.
This document presents the target selection process for the first year of the Breakthrough Listen search for intelligent life using the Green Bank Telescope, Parkes Telescope, and Automated Planet Finder. The targets include: 1) The 60 nearest stars within 5.1 parsecs to search for faint signals; 2) 1649 stars spanning stellar types from the Hipparcos catalog; 3) 123 nearby galaxies representing different morphological types to search billions of stars simultaneously; and 4) several classes of exotic objects like white dwarfs and neutron stars. The telescopes will observe 1,000,000 stars and galaxies at radio and optical wavelengths between 350 MHz to 100 GHz and 374-950nm, respectively, to search for technological signals.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
Four new planets_around_giant_stars_and_the_mass_metallicity_correlation_of_p...Sérgio Sacani
Exoplanet searches have revealed interesting correlations between the stellar properties and the occurrence rate of planets.
In particular, different independent surveys have demonstrated that giant planets are preferentially found around metal-rich stars and
that their fraction increases with the stellar mass.
Aims. During the past six years, we have conducted a radial velocity follow-up program of 166 giant stars, to detect substellar
companions, and characterizing their orbital properties. Using this information, we aim to study the role of the stellar evolution in
the orbital parameters of the companions, and to unveil possible correlations between the stellar properties and the occurrence rate of
giant planets.
Methods. We have taken multi-epoch spectra using FEROS and CHIRON for all of our targets, from which we have computed
precision radial velocities and we have derived atmospheric and physical parameters. Additionally, velocities computed from UCLES
spectra are presented here. By studying the periodic radial velocity signals, we have detected the presence of several substellar
companions.
Results. We present four new planetary systems around the giant stars HIP8541, HIP74890, HIP84056 and HIP95124. Additionally,
we study the correlation between the occurrence rate of giant planets with the stellar mass and metallicity of our targets. We find that
giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7+15.5
−5.9 % around stars with [Fe/H] ∼
0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆∼ 1.0 - 2.1 M⊙ ,
with a maximum of f = 13.0+10.1
−4.2 %, at M⋆= 2.1 M⊙ .
Conclusions. We conclude that giant planets are preferentially formed around metal-rich stars. Also, we conclude that they are more
efficiently formed around more massive stars, in the stellar mass range of ∼ 1.0 - 2.1 M⊙ . These observational results confirm previous
findings for solar-type and post-MS hosting stars, and provide further support to the core-accretion formation model.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
VISIONS: The VISTA Star Formation AtlasSérgio Sacani
The VISIONS survey observed five nearby star-forming regions in the near-infrared using the VISTA telescope over a period of 5 years. It collected 1.15 million images totaling 19 TB of raw data. The survey was designed to build an infrared legacy archive similar to 2MASS but probing embedded objects. It used three subsurveys - a wide subsurvey with shallow observations covering large areas, a deep subsurvey targeting regions of high dust extinction, and a control subsurvey of low extinction areas. The goal was to characterize young stellar objects, study stellar and cluster formation and evolution, and measure proper motions to complement the Gaia mission.
Chiotelis Ioannis, Theodoropoulou Maria, “Searching for Black Holes. Photometry in our Classrooms”, Hellenic Conference on Innovating STEM Education, 16-18 December 2016, Athens, Greece.
A Search for Technosignatures Around 11,680 Stars with the Green Bank Telesco...Sérgio Sacani
We conducted a search for narrowband radio signals over four observing sessions in 2020–2023 with
the L-band receiver (1.15–1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the
telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of
∼11,860 stars and planetary systems in the ∼9 arcminute beam of the telescope. All detections were
either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. In
this work, we also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection
and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable
frequency range of the receiver and 98.7% of the injections when regions of dense RFI are excluded. In
another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ∼15 times
smaller at ∼6%. The pipeline efficiency affects SETI search volume calculations as well as calculations
of upper bounds on the number of transmitting civilizations. We developed an improved Drake Figure
of Merit for SETI search volume calculations that includes the pipeline efficiency and frequency drift
rate coverage. Based on our observations, we found that there is a high probability (94.0–98.7%) that
fewer than ∼0.014% of stars earlier than M8 within 100 pc host a transmitter that is detectable in
our search (EIRP > 1012 W). Finally, we showed that the UCLA SETI pipeline natively detects the
signals detected with AI techniques by Ma et al. (2023).
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
AT 2022aedm and a New Class of Luminous, Fast-cooling Transients in Elliptica...Sérgio Sacani
This document reports the discovery and follow-up observations of a remarkable fast-evolving optical transient called AT 2022aedm. Key points:
- AT 2022aedm was discovered by the ATLAS survey and reached an extremely luminous peak magnitude of Mg ≈ -22 mag.
- It exhibited an unusually fast rise time of 9 days and faded by 2 magnitudes in the following 15 days.
- Most surprisingly, its host galaxy was found to be a massive elliptical galaxy with negligible star formation.
- Extensive follow-up observations including spectroscopy found it shared properties with two other similar transients in passive galaxies, suggesting a new class of "luminous fast coolers." However
Two temperate Earth-mass planets orbiting the nearby star GJ 1002Sérgio Sacani
We report the discovery and characterisation of two Earth-mass planets orbiting in the habitable zone of the nearby M-dwarf GJ 1002 based on
the analysis of the radial-velocity (RV) time series from the ESPRESSO and CARMENES spectrographs. The host star is the quiet M5.5 V star
GJ 1002 (relatively faint in the optical, V ∼ 13.8 mag, but brighter in the infrared, J ∼ 8.3 mag), located at 4.84 pc from the Sun.
We analyse 139 spectroscopic observations taken between 2017 and 2021. We performed a joint analysis of the time series of the RV and full-width
half maximum (FWHM) of the cross-correlation function (CCF) to model the planetary and stellar signals present in the data, applying Gaussian
process regression to deal with the stellar activity.
We detect the signal of two planets orbiting GJ 1002. GJ 1002 b is a planet with a minimum mass mp sin i of 1.08 ± 0.13 M⊕ with an orbital period
of 10.3465 ± 0.0027 days at a distance of 0.0457 ± 0.0013 au from its parent star, receiving an estimated stellar flux of 0.67 F⊕. GJ 1002 c is a
planet with a minimum mass mp sin i of 1.36 ± 0.17 M⊕ with an orbital period of 20.202 ± 0.013 days at a distance of 0.0738 ± 0.0021 au from
its parent star, receiving an estimated stellar flux of 0.257 F⊕. We also detect the rotation signature of the star, with a period of 126 ± 15 days. We
find that there is a correlation between the temperature of certain optical elements in the spectrographs and changes in the instrumental profile that
can affect the scientific data, showing a seasonal behaviour that creates spurious signals at periods longer than ∼ 200 days.
GJ 1002 is one of the few known nearby systems with planets that could potentially host habitable environments. The closeness of the host star
to the Sun makes the angular sizes of the orbits of both planets (∼ 9.7 mas and ∼ 15.7 mas, respectively) large enough for their atmosphere to be
studied via high-contrast high-resolution spectroscopy with instruments such as the future spectrograph ANDES for the ELT or the LIFE mission.
The curiosity to find earth-like planet can be dated to long time ago. But because of the incapability of the available technologies, it was a dream to detect planets beyond our solar system. After the time stated, the space research have taken a new leap and opened a new era of information. The concept of Exoplanet born. It can also be referred to as Extra Solar Planet. Any planet which is not within our solar system is Exoplanet. But an absolute definition is quite complex and problematic. So some of the important characteristics of an Exoplanet is it has to be earth-like environment, it can be giant or terrestrial type
The curiosity to find earth-like planet can be dated to long time ago. But because of the incapability of the available technologies, it was a dream to detect planets beyond our solar system. After the time stated, the space research have taken a new leap and opened a new era of information. The concept of Exoplanet born. It can also be referred to as Extra Solar Planet. Any planet which is not within our solar system is Exoplanet. But an absolute definition is quite complex and problematic. So some of the important characteristics of an Exoplanet is it has to be earth-like environment, it can be giant or terrestrial type
The Surprising Evolution of the Shadow on the TW Hya DiskSérgio Sacani
We report new total-intensity visible-light high-contrast imaging of the TW Hya disk taken with the Space
Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. This represents the first published
images of the disk with STIS since 2016, when a moving shadow on the disk surface was reported. We continue
to see the shadow moving in a counterclockwise fashion, but in these new images the shadow has evolved into
two separate shadows, implying a change in behavior for the occulting structure. Based on radiative-transfer
models of optically thick disk structures casting shadows, we infer that a plausible explanation for the change is
that there are now two misaligned components of the inner disk. The first of these disks is located between 5 and
6 au with an inclination of 5.5° and position angle (PA) of 170°, and the second between 6 and 7 au with
an inclination of 7° and PA of 50°. Finally, we speculate on the implications of the new shadow structure
and determine that additional observations are needed to disentangle the nature of TW Hya’s inner-disk
architecture.
The harps n-rocky_planet_search_hd219134b_transiting_rocky_planetSérgio Sacani
Usando o espectrógrafo HARPS-N acoplado ao Telescopio Nazionale Galileo no Observatório de Roque de Los Muchachos, nas Ilhas Canárias, os astrônomos descobriram três exoplanetas, classificados como Super-Terras e um gigante gasoso orbitando uma estrela próxima, chamada de HD 219134.
A HD 219134, também conhecida como HR 8832 é uma estrela do tipo anã-K de quinta magnitude, localizada a aproximadamente 21 anos-luz de distância da Terra, na constelação de Cassiopeia.
A estrela é levemente mais fria e menos massiva que o nosso sol. Ela é tão brilhante que pode ser observada a olho nu.
O sistema planetário HD 219134, abriga um planeta gigante gasoso externo e três planetas internos classificados como super-Terras, um dos quais transita em frente à estrela.
Observation of large scale precursor correlations between cosmic rays and ear...Sérgio Sacani
The search for correlations between secondary cosmic ray detection rates and seismic
effects has long been a subject of investigation motivated by the hope of identifying a new
precursor type that could feed a global early warning system against earthquakes. Here we show
for the first time that the average variation of the cosmic ray detection rates correlates with the
global seismic activity to be observed with a time lag of approximately two weeks, and that the
significance of the effect varies with a periodicity resembling the undecenal solar cycle, with a
shift in phase of around three years, exceeding 6 𝜎 at local maxima. The precursor characteristics
of the observed correlations point to a pioneer perspective of an early warning system against
earthquakes.
Jupiter’s interior and deep atmosphere: The initial pole-to-pole passes with ...Sérgio Sacani
On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter,
passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter’s
poles show a chaotic scene, unlike Saturn’s poles. Microwave sounding reveals weather
features at pressures deeper than 100 bars, dominated by an ammonia-rich, narrow
low-latitude plume resembling a deeper, wider version of Earth’s Hadley cell. Near-infrared
mapping reveals the relative humidity within prominent downwelling regions. Juno’s
measured gravity field differs substantially from the last available estimate and is one
order of magnitude more precise. This has implications for the distribution of heavy
elements in the interior, including the existence and mass of Jupiter’s core. The observed
magnetic field exhibits smaller spatial variations than expected, indicative of a rich
harmonic content.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
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This document summarizes the discovery of a transiting circumbinary planet (PH1) in a quadruple star system by volunteers with the Planet Hunters citizen science project. PH1 orbits outside a 20-day eclipsing binary consisting of an F dwarf and an M dwarf star. It has a radius of 6.18 ± 0.17 R⊕ and an upper mass limit of 169 M⊕. Beyond PH1's orbit is a distant visual binary bound to the system, making this the first known case of a transiting planet in a quadruple star configuration. Planet Hunters volunteers identified transit features in the Kepler light curve of KIC 4862625 through visual inspection and discussion, leading to the confirmation and characterization
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
This summarizes a scientific study on long-distance quantum teleportation between two laboratories separated by 55 meters but connected by 2 kilometers of fiber optic cable. The key points are:
1) Researchers teleported quantum states (qubits) carried by photons at 1.3 micrometer wavelengths onto photons at 1.55 micrometer wavelengths between the two laboratories.
2) The qubits were encoded in time-bin superpositions and entanglement rather than polarization to make them more robust against decoherence in optical fibers.
3) A partial Bell state measurement was performed using linear optics at the receiving end to probabilistically teleport the quantum states over the long distance.
This document presents the target selection process for the first year of the Breakthrough Listen search for intelligent life using the Green Bank Telescope, Parkes Telescope, and Automated Planet Finder. The targets include: 1) The 60 nearest stars within 5.1 parsecs to search for faint signals; 2) 1649 stars spanning stellar types from the Hipparcos catalog; 3) 123 nearby galaxies representing different morphological types to search billions of stars simultaneously; and 4) several classes of exotic objects like white dwarfs and neutron stars. The telescopes will observe 1,000,000 stars and galaxies at radio and optical wavelengths between 350 MHz to 100 GHz and 374-950nm, respectively, to search for technological signals.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
Four new planets_around_giant_stars_and_the_mass_metallicity_correlation_of_p...Sérgio Sacani
Exoplanet searches have revealed interesting correlations between the stellar properties and the occurrence rate of planets.
In particular, different independent surveys have demonstrated that giant planets are preferentially found around metal-rich stars and
that their fraction increases with the stellar mass.
Aims. During the past six years, we have conducted a radial velocity follow-up program of 166 giant stars, to detect substellar
companions, and characterizing their orbital properties. Using this information, we aim to study the role of the stellar evolution in
the orbital parameters of the companions, and to unveil possible correlations between the stellar properties and the occurrence rate of
giant planets.
Methods. We have taken multi-epoch spectra using FEROS and CHIRON for all of our targets, from which we have computed
precision radial velocities and we have derived atmospheric and physical parameters. Additionally, velocities computed from UCLES
spectra are presented here. By studying the periodic radial velocity signals, we have detected the presence of several substellar
companions.
Results. We present four new planetary systems around the giant stars HIP8541, HIP74890, HIP84056 and HIP95124. Additionally,
we study the correlation between the occurrence rate of giant planets with the stellar mass and metallicity of our targets. We find that
giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7+15.5
−5.9 % around stars with [Fe/H] ∼
0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆∼ 1.0 - 2.1 M⊙ ,
with a maximum of f = 13.0+10.1
−4.2 %, at M⋆= 2.1 M⊙ .
Conclusions. We conclude that giant planets are preferentially formed around metal-rich stars. Also, we conclude that they are more
efficiently formed around more massive stars, in the stellar mass range of ∼ 1.0 - 2.1 M⊙ . These observational results confirm previous
findings for solar-type and post-MS hosting stars, and provide further support to the core-accretion formation model.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
VISIONS: The VISTA Star Formation AtlasSérgio Sacani
The VISIONS survey observed five nearby star-forming regions in the near-infrared using the VISTA telescope over a period of 5 years. It collected 1.15 million images totaling 19 TB of raw data. The survey was designed to build an infrared legacy archive similar to 2MASS but probing embedded objects. It used three subsurveys - a wide subsurvey with shallow observations covering large areas, a deep subsurvey targeting regions of high dust extinction, and a control subsurvey of low extinction areas. The goal was to characterize young stellar objects, study stellar and cluster formation and evolution, and measure proper motions to complement the Gaia mission.
Chiotelis Ioannis, Theodoropoulou Maria, “Searching for Black Holes. Photometry in our Classrooms”, Hellenic Conference on Innovating STEM Education, 16-18 December 2016, Athens, Greece.
A Search for Technosignatures Around 11,680 Stars with the Green Bank Telesco...Sérgio Sacani
We conducted a search for narrowband radio signals over four observing sessions in 2020–2023 with
the L-band receiver (1.15–1.73 GHz) of the 100 m diameter Green Bank Telescope. We pointed the
telescope in the directions of 62 TESS Objects of Interest, capturing radio emissions from a total of
∼11,860 stars and planetary systems in the ∼9 arcminute beam of the telescope. All detections were
either automatically rejected or visually inspected and confirmed to be of anthropogenic nature. In
this work, we also quantified the end-to-end efficiency of radio SETI pipelines with a signal injection
and recovery analysis. The UCLA SETI pipeline recovers 94.0% of the injected signals over the usable
frequency range of the receiver and 98.7% of the injections when regions of dense RFI are excluded. In
another pipeline that uses incoherent sums of 51 consecutive spectra, the recovery rate is ∼15 times
smaller at ∼6%. The pipeline efficiency affects SETI search volume calculations as well as calculations
of upper bounds on the number of transmitting civilizations. We developed an improved Drake Figure
of Merit for SETI search volume calculations that includes the pipeline efficiency and frequency drift
rate coverage. Based on our observations, we found that there is a high probability (94.0–98.7%) that
fewer than ∼0.014% of stars earlier than M8 within 100 pc host a transmitter that is detectable in
our search (EIRP > 1012 W). Finally, we showed that the UCLA SETI pipeline natively detects the
signals detected with AI techniques by Ma et al. (2023).
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
AT 2022aedm and a New Class of Luminous, Fast-cooling Transients in Elliptica...Sérgio Sacani
This document reports the discovery and follow-up observations of a remarkable fast-evolving optical transient called AT 2022aedm. Key points:
- AT 2022aedm was discovered by the ATLAS survey and reached an extremely luminous peak magnitude of Mg ≈ -22 mag.
- It exhibited an unusually fast rise time of 9 days and faded by 2 magnitudes in the following 15 days.
- Most surprisingly, its host galaxy was found to be a massive elliptical galaxy with negligible star formation.
- Extensive follow-up observations including spectroscopy found it shared properties with two other similar transients in passive galaxies, suggesting a new class of "luminous fast coolers." However
Two temperate Earth-mass planets orbiting the nearby star GJ 1002Sérgio Sacani
We report the discovery and characterisation of two Earth-mass planets orbiting in the habitable zone of the nearby M-dwarf GJ 1002 based on
the analysis of the radial-velocity (RV) time series from the ESPRESSO and CARMENES spectrographs. The host star is the quiet M5.5 V star
GJ 1002 (relatively faint in the optical, V ∼ 13.8 mag, but brighter in the infrared, J ∼ 8.3 mag), located at 4.84 pc from the Sun.
We analyse 139 spectroscopic observations taken between 2017 and 2021. We performed a joint analysis of the time series of the RV and full-width
half maximum (FWHM) of the cross-correlation function (CCF) to model the planetary and stellar signals present in the data, applying Gaussian
process regression to deal with the stellar activity.
We detect the signal of two planets orbiting GJ 1002. GJ 1002 b is a planet with a minimum mass mp sin i of 1.08 ± 0.13 M⊕ with an orbital period
of 10.3465 ± 0.0027 days at a distance of 0.0457 ± 0.0013 au from its parent star, receiving an estimated stellar flux of 0.67 F⊕. GJ 1002 c is a
planet with a minimum mass mp sin i of 1.36 ± 0.17 M⊕ with an orbital period of 20.202 ± 0.013 days at a distance of 0.0738 ± 0.0021 au from
its parent star, receiving an estimated stellar flux of 0.257 F⊕. We also detect the rotation signature of the star, with a period of 126 ± 15 days. We
find that there is a correlation between the temperature of certain optical elements in the spectrographs and changes in the instrumental profile that
can affect the scientific data, showing a seasonal behaviour that creates spurious signals at periods longer than ∼ 200 days.
GJ 1002 is one of the few known nearby systems with planets that could potentially host habitable environments. The closeness of the host star
to the Sun makes the angular sizes of the orbits of both planets (∼ 9.7 mas and ∼ 15.7 mas, respectively) large enough for their atmosphere to be
studied via high-contrast high-resolution spectroscopy with instruments such as the future spectrograph ANDES for the ELT or the LIFE mission.
The curiosity to find earth-like planet can be dated to long time ago. But because of the incapability of the available technologies, it was a dream to detect planets beyond our solar system. After the time stated, the space research have taken a new leap and opened a new era of information. The concept of Exoplanet born. It can also be referred to as Extra Solar Planet. Any planet which is not within our solar system is Exoplanet. But an absolute definition is quite complex and problematic. So some of the important characteristics of an Exoplanet is it has to be earth-like environment, it can be giant or terrestrial type
The curiosity to find earth-like planet can be dated to long time ago. But because of the incapability of the available technologies, it was a dream to detect planets beyond our solar system. After the time stated, the space research have taken a new leap and opened a new era of information. The concept of Exoplanet born. It can also be referred to as Extra Solar Planet. Any planet which is not within our solar system is Exoplanet. But an absolute definition is quite complex and problematic. So some of the important characteristics of an Exoplanet is it has to be earth-like environment, it can be giant or terrestrial type
The Surprising Evolution of the Shadow on the TW Hya DiskSérgio Sacani
We report new total-intensity visible-light high-contrast imaging of the TW Hya disk taken with the Space
Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. This represents the first published
images of the disk with STIS since 2016, when a moving shadow on the disk surface was reported. We continue
to see the shadow moving in a counterclockwise fashion, but in these new images the shadow has evolved into
two separate shadows, implying a change in behavior for the occulting structure. Based on radiative-transfer
models of optically thick disk structures casting shadows, we infer that a plausible explanation for the change is
that there are now two misaligned components of the inner disk. The first of these disks is located between 5 and
6 au with an inclination of 5.5° and position angle (PA) of 170°, and the second between 6 and 7 au with
an inclination of 7° and PA of 50°. Finally, we speculate on the implications of the new shadow structure
and determine that additional observations are needed to disentangle the nature of TW Hya’s inner-disk
architecture.
The harps n-rocky_planet_search_hd219134b_transiting_rocky_planetSérgio Sacani
Usando o espectrógrafo HARPS-N acoplado ao Telescopio Nazionale Galileo no Observatório de Roque de Los Muchachos, nas Ilhas Canárias, os astrônomos descobriram três exoplanetas, classificados como Super-Terras e um gigante gasoso orbitando uma estrela próxima, chamada de HD 219134.
A HD 219134, também conhecida como HR 8832 é uma estrela do tipo anã-K de quinta magnitude, localizada a aproximadamente 21 anos-luz de distância da Terra, na constelação de Cassiopeia.
A estrela é levemente mais fria e menos massiva que o nosso sol. Ela é tão brilhante que pode ser observada a olho nu.
O sistema planetário HD 219134, abriga um planeta gigante gasoso externo e três planetas internos classificados como super-Terras, um dos quais transita em frente à estrela.
Observation of large scale precursor correlations between cosmic rays and ear...Sérgio Sacani
The search for correlations between secondary cosmic ray detection rates and seismic
effects has long been a subject of investigation motivated by the hope of identifying a new
precursor type that could feed a global early warning system against earthquakes. Here we show
for the first time that the average variation of the cosmic ray detection rates correlates with the
global seismic activity to be observed with a time lag of approximately two weeks, and that the
significance of the effect varies with a periodicity resembling the undecenal solar cycle, with a
shift in phase of around three years, exceeding 6 𝜎 at local maxima. The precursor characteristics
of the observed correlations point to a pioneer perspective of an early warning system against
earthquakes.
Jupiter’s interior and deep atmosphere: The initial pole-to-pole passes with ...Sérgio Sacani
On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter,
passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter’s
poles show a chaotic scene, unlike Saturn’s poles. Microwave sounding reveals weather
features at pressures deeper than 100 bars, dominated by an ammonia-rich, narrow
low-latitude plume resembling a deeper, wider version of Earth’s Hadley cell. Near-infrared
mapping reveals the relative humidity within prominent downwelling regions. Juno’s
measured gravity field differs substantially from the last available estimate and is one
order of magnitude more precise. This has implications for the distribution of heavy
elements in the interior, including the existence and mass of Jupiter’s core. The observed
magnetic field exhibits smaller spatial variations than expected, indicative of a rich
harmonic content.
Similar to A Deep and Wide Twilight Survey for Asteroids Interior to Earth and Venus (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
Travis Hills' Endeavors in Minnesota: Fostering Environmental and Economic Pr...Travis Hills MN
Travis Hills of Minnesota developed a method to convert waste into high-value dry fertilizer, significantly enriching soil quality. By providing farmers with a valuable resource derived from waste, Travis Hills helps enhance farm profitability while promoting environmental stewardship. Travis Hills' sustainable practices lead to cost savings and increased revenue for farmers by improving resource efficiency and reducing waste.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
Unlocking the mysteries of reproduction: Exploring fecundity and gonadosomati...AbdullaAlAsif1
The pygmy halfbeak Dermogenys colletei, is known for its viviparous nature, this presents an intriguing case of relatively low fecundity, raising questions about potential compensatory reproductive strategies employed by this species. Our study delves into the examination of fecundity and the Gonadosomatic Index (GSI) in the Pygmy Halfbeak, D. colletei (Meisner, 2001), an intriguing viviparous fish indigenous to Sarawak, Borneo. We hypothesize that the Pygmy halfbeak, D. colletei, may exhibit unique reproductive adaptations to offset its low fecundity, thus enhancing its survival and fitness. To address this, we conducted a comprehensive study utilizing 28 mature female specimens of D. colletei, carefully measuring fecundity and GSI to shed light on the reproductive adaptations of this species. Our findings reveal that D. colletei indeed exhibits low fecundity, with a mean of 16.76 ± 2.01, and a mean GSI of 12.83 ± 1.27, providing crucial insights into the reproductive mechanisms at play in this species. These results underscore the existence of unique reproductive strategies in D. colletei, enabling its adaptation and persistence in Borneo's diverse aquatic ecosystems, and call for further ecological research to elucidate these mechanisms. This study lends to a better understanding of viviparous fish in Borneo and contributes to the broader field of aquatic ecology, enhancing our knowledge of species adaptations to unique ecological challenges.
2. cross Earth’s orbit such as Aten and Apollo NEOs with
semimajor axes interior and exterior to Earth, respectively
(Mainzer et al. 2014; Schunova-Lilly et al. 2017; Morbidelli
et al. 2020).
Understanding the relative populations of objects with orbits
interior to Earth versus exterior to Earth will help us understand
how objects are transported throughout the inner solar system
(Strom et al. 2015). In addition, disruption processes of NEOs,
such as fragmenting from thermal stresses, breaking up from
rotational excitation, or tidal disruption from passing near the
Sun or planets can be analyzed by comparing the predicted
number of NEOs found interior to Earth versus exterior to
Earth and correlating this with the composition or type of
objects found (Granvik et al. 2016). Such correlations and
analysis will further yield insights into the structure and
strength of the different types of NEO classes. Various internal
stresses on NEOs such as tidal deformation and solar heating
will cause more fragile asteroid compositions and structures to
erode or break-up as they approach the planets and Sun (Li &
Jewitt 2013; Ye & Granvik 2019).
In addition to NEOs, which are strongly influenced by the
Earth, some objects found interior to Earth’s orbit may exhibit
strong influences from Venus. There are a few known well
observed asteroids that have orbital periods similar to Venus’:
(322756) 2001 CK32, (524522) 2002 VE68, 2012 XE133,
2013 ND15, and 2015 WZ12 as well as some more recently
discovered NEOs with semimajor axes near Venus’ between
0.722 and 0.725 au: 2020 BT2, 2020 CL1, 2020 QU5, 2021
XA1, 2021 XO3, 2022 BL5, and 2022 CD (see Figures 1 and
2). All of these near-Venus co-orbital asteroids are dynamically
unstable on million year timescales since they have high-
eccentricity orbits that cross the orbit of the Earth (Mikkola
et al. 2004; de la Fuente Marcos & de la Fuente
Marcos 2012, 2013, 2014, 2017). The same situation has been
found for the known co-orbitals of Earth (Brasser et al. 2004;
Connors et al. 2011; Hui et al. 2021; Santana-Ros et al. 2022).
The population of low-eccentricity Venus and Earth co-orbitals
that are stable resonant objects may be small due to
perturbations from terrestrial planets or nongravitational effects
(Morais & Morbidelli 2006; Malhotra 2019; Pokorny &
Kuchner 2021). There are no known satellites of Venus, likely
because the Hill sphere of Venus is mostly dynamically
unstable to long term satellites (Sheppard & Trujillo 2009). To
date, the population of 1 km and smaller objects near Venus’
orbit is relatively unconstrained observationally as most
surveys in this region are only sensitive to larger objects.
Data from the two space missions HELIOS and STEREO
indicate the presence of a narrow ring of dust in Venus’ orbit
(Leinert & Moster 2007; Jones et al. 2013). This Venus co-
orbital dust ring could come from a population of low-
eccentricity (e < 0.3) stable Venus resonant co-orbital objects
(Pokorny & Kuchner 2019). These authors also found that
about 8% of an initial population of Venus resonant objects
remain stable for the age of the solar system. Thus, these
putative low-eccentricity Venus resonant co-orbitals could be
the leftover remnants of the planetesimals that formed near
Venus, unlike most NEOs and high-eccentricity Venus co-
orbitals that are believed to have recently escaped from the
much further out main asteroid belt (Granvik et al. 2017). This
theorized population of low-eccentricity Venus resonant
objects has yet to be observationally ruled out since most
surveys to date have not covered the large areas of sky to the
faint depths needed to find such a population of low-
eccentricity objects interior to Earth. This population could
be too faint for small class telescopes to detect efficiently in the
glare of the Sun as objects less than about 1 km in size would
mostly be fainter than about 20th magnitude (Morbidelli et al.
2020; Masiero et al. 2020).
Surveys that have covered a significant portion of the sky
looking for asteroids near Venus have used small class
Figure 1. Known NEOs plotted with semimajor axis vs. eccentricity. The new discoveries from this survey are shown by big blue circles. The yellow area shows the
region near Venus’ orbit that dynamcially stable low-eccentricity Venus co-orbitals would be expected to be found, where no asteroid is known. All known asteroids
with semimajor axes similar to Venus are on dynamically unstable, highly eccentric orbits that cross Earth’s orbit (small green circles). Atira-type object orbits remain
interior to Earth’s orbit, shown as red circles to the left of the vertical dashed line starting at 1 au, which is the inner edge of the Earth crossing zone.
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The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
3. telescopes (Myhrvold 2016). Recently the 48 inch telescope
Zwicky Transient Facility (ZTF; Ye et al. 2020) survey has
done the most extensive search for asteroids near Venus. ZTF
found the first ever asteroid that has an orbit entirely interior to
Venus, (594913) ’Ayló’chaxnim (2020 AV2; Bolin et al.
2020), though the orbit is only stable for a few million years
(Greenstreet 2020; de la Fuente Marcos & de la Fuente
Marcos 2020; Bolin et al. 2022). This survey has covered
several thousand square degrees of sky interior to Earth’s orbit,
but is limited in its discovery ability of smaller objects as it uses
a 1.2 m telescope (Ye et al. 2020). Based on ’Ayló’chaxnim’s
absolute magnitude, it is likely a relatively large asteroid of
∼1.5 km in size.
We performed a pilot survey in 2019 September to
determine if a search for objects near Venus’ orbit is feasible
with the medium class Blanco 4 m telescope using the large
field-of-view Dark Energy Camera (DECam), which is the
largest sky area camera on a 4 m or larger telescope. We
searched about 35 square degrees of sky some 40°–50° in
elongation away from the Sun near the end of nautical and start
of astronomical twilight time in the evening. The images went
to over 21st mag in the r band and we were able to put some
moderate limits on the size of any stable Venus resonant co-
orbital population (Pokorny et al. 2020). Here we discuss an
additional 589 square degrees of twilight sky near to and
interior to Venus’ orbit, yielding a total of 624 square degrees
searched in the survey to date.
2. Observations
The twilight survey for objects near to and interior to Venus’
orbit uses the DECam on the Cerro-Tololo Inter-American
Observatory (CTIO) 4 meter Blanco telescope in Chile.
DECam has 61 working science CCDs arranged in a circular
type pattern at the prime focus of the telescope. Each CCD has
2048 × 4096 pixels with a pixel scale of about 0.264
arcseconds, yielding a field of view of about 2.7 square
degrees per image (Flaugher et al. 2015). Images were
calibrated by subtracting a median bias image and divided by
a median dome flat.
Observations were obtained just after nautical twilight ends
in the evening and just before nautical twilight begins in the
morning. The Sun is usually between about −15 and −12
degrees below the horizon when the images are taken, giving
about 10 minutes of observation time each twilight. Images
were generally taken at airmasses between about 2.3 and 2.5,
near the 23° elevation limit of the telescope. Most fields were
observed near to or interior to Venus’ orbit when projected
onto the sky (Figure 3). The r-band filter with an exposure time
of 28 s was used. With simultaneous readout and offsetting the
telescope to the next position a few degrees away, it takes just
under 1 minute between the start of two successive images.
Two images of each field are taken separated by about 2–4
minutes. The images usually only had a background of a few
Figure 2. Same as Figure 1 but using inclination.
Figure 3. The twilight survey fields taken with DECam showing their
elongation position from the Sun and inclination from the ecliptic. The
maximum elongation from the Sun to Mercury and Venus are shown by
vertical dotted and dashed lines, respectively.
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The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
4. thousand counts, while the detector does not saturate until
several tens of thousands of counts.
The depth of each image mostly depends on the seeing and
the sky brightness. The signal-to-noise ratio of asteroids in the
twilight images is generally worse than when observed exterior
to Earth’s orbit because of the high phase angles of the
asteroids, bright background sky, and high airmass. In the
twilight images taken near the Sun, the main belt asteriods are
much farther away in our fields than when imaged in darker
skies exterior to Earth’s orbit. Thus, because of the relatively
large distances of the main belt asteroids, our survey will not
usually find unknown main belt asteroids.
An object that is interior to Earth’s orbit will generally have
an apparent motion of over 100 arcseconds per hour, with
objects near Venus’ orbit expected to show motions near 150
arcseconds per hour (Figure 4). The exposure time is limited by
the fast motion of the objects, as an object with an apparent
motion of 150 arcseconds per hour will start to show significant
trailing after about 30 s. The survey used 28 s for the exposure
time to limit any signal-to-noise trailing losses of the asteroids.
The moving object search algorithm was the same as that used
to find outer solar system objects (Trujillo et al. 2001; Sheppard
et al. 2019) and it was set to flag any objects that were found to
have an apparent motion faster than 75 arcseconds per hour.
This allows us to identify easily the objects of interest that could
be NEOs or Venus resonant co-orbitals while rejecting the many
objects within the main asteroid belt and beyond, as their
apparent motion is less than about 80 arcseconds per hour. Since
some main belt asteroids have apparent motions faster than our
75 arcsecond per hour lower limit, we used the known main belt
asteroids that we detected moving faster than 75 arcseconds per
hour to help characterize our survey’s detection efficiency.
We determined the limiting magnitude or depth to find
moving objects in our survey fields based on two techniques.
First, we determined to what magnitude we detected known
main belt asteroids as well as known NEOs. Second, we
implanted artificial moving objects into some fields to
determine our moving object detection efficiency. The
techniques are complementary and agreed to within a tenth
of a magnitude of each other. The known main belt asteroids
had their V-band Minor Planet Center magnitudes converted to
r-band magnitudes using the simple conversion V − r = 0.2
mag (Smith et al. 2002; Sheppard 2012; Sergeyev &
Carry 2021). Artificial objects were placed in some of the
fields ranging from 19th to 23rd mag in the r band with
apparent motions as expected for NEOs between 80 and 170
arcseconds per hour. Because of the short time-base of only ∼4
minutes between images and the short integration time of 28 s,
we found no significant differences in our detection of objects
with the fastest or slowest apparent motions.
We find that for the average field with a seeing of about 1 4,
we detected about 50% of artificially implanted objects for
mr ∼ 21.3 mag, which is what we take as the overall limiting
magnitude of the survey, though different nights had different
limiting magnitudes as shown in Table 1 and Figure 5, with
some of the best seeing fields reaching nearly 22nd mag in depth.
The detection efficiency curve has a similar shape each night as
shown in Figure 6, just shifted in mr to the value as shown in
Table 1, which mostly depended on the seeing. Figure 5 shows
the limiting magnitude of each field versus the elongation of the
field from the Sun. The survey was able to detect asteroids near
Venus’ orbit of only a few hundred meters in size assuming
moderate albedos like S-type asteroids (Pokorny et al. 2020).
From Jedicke et al. (2016) we use Equation (15) to fit
the detection efficiency curve shown in Figure 6: ( )
mr =
[ ( )]
m r r
1 exp
o r 50% width
1
+ - -
, where r50% is the magnitude
in the r band where the efficiency is 50%, òo is the maximum
survey efficiency (i.e., the brightest object efficiency), and
rwidth is the magnitude range in mr that the efficiency decreases
from near 75% to 25%. We find òo = 0.95 ± 0.01, r50% = 21.3,
and rwidth = 0.19.
As the survey was active every few nights, most of the
asteroid recovery of new discoveries was done using DECam.
D. Tholen also recovered new discoveries with the University
of Hawaii 88 inch telescope and the Canada-France-Hawaii 3.6
m telescope (CFHT). The 6.5 m Baade–Magellan telescope at
Las Campanas in Chile was also used in recovery observations
as was the 1 meter global network of telescopes operated by
Las Cumbres Observatory, mainly through the European Space
Agency’s (ESA) Planetary Defense Office (PDO).
Figure 4. The R.A. and decl. of a hypothetical population of low-eccentricity, low-inclination, stable Venus co-orbital asteroids (Pokorny & Kuchner 2019) as they
would appear on 2020 September 30 at 23:30 UT. Objects near Venus’ orbit well interior to Earth’s orbit would appear to move faster than about 100 arcseconds per
hour, distinguishing them from more distant main belt asteroids that tend to move slower than 80 arcseconds per hour. The red dot shows Venus’ location.
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The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
8. 3. Results
Using DECam, we covered 624 square degrees of sky near
to and interior to Venus’ orbit. Three new NEOs were
discovered, with two likely being about 1 km or larger in size
(Table 2). In addition, we serendipitously detected several
known NEOs moving well over 90 arcseconds per hour,
including Atira-, Aten-, Amor-, and Apollo-type NEOs, with
several being Potentially Hazardous Asteroids (PHAs).
3.1. 2021 PH27: Atira Type
Asteroid 2021 PH27 was discovered by S. Sheppard on 2021
August 13 in twilight images taken near the Sun by the Local
Table 1
(Continued)
R.A.(J2000) Decl.(J2000) UT Date Limiting Seeing
hh:mm:ss dd:mm:ss YYYY/MM/DD/hh:mm (mag) (arcseconds)
15:04:00 −28:00:00 2021/12/24/08:25 21.4 1.1
15:07:00 −29:30:00 2021/12/24/08:26 21.4 1.1
15:08:00 −31:15:00 2021/12/24/08:27 21.4 1.1
15:13:00 −33:00:00 2021/12/24/08:31 21.1 1.1
15:26:00 −34:00:00 2021/12/28/08:28 21.6 1.2
15:26:30 −35:30:00 2021/12/28/08:29 21.6 1.2
15:27:00 −37:00:00 2021/12/28/08:30 21.6 1.2
15:32:00 −38:30:00 2021/12/28/08:34 21.3 1.2
15:40:00 −40:00:00 2021/12/31/08:30 21.8 1.1
15:40:30 −41:40:00 2021/12/31/08:31 21.8 1.1
15:41:30 −43:30:00 2021/12/31/08:32 21.8 1.1
15:47:00 −45:00:00 2021/12/31/08:35 21.5 1.1
22:07:00 −20:00:00 2022/01/03/00:52 21.1 1.2
15:37:00 −20:00:00 2022/01/03/08:34 22.0 1.1
15:41:00 −21:30:00 2022/01/03/08:35 22.0 1.1
15:45:00 −23:00:00 2022/01/03/08:36 21.9 1.1
15:51:00 −24:30:00 2022/01/03/08:41 21.6 1.1
16:02:00 −26:00:00 2022/01/06/08:34 22.0 0.9
16:05:30 −27:30:00 2022/01/06/08:35 22.0 0.9
16:08:30 −29:00:00 2022/01/06/08:36 21.9 0.9
16:14:00 −30:30:00 2022/01/06/08:40 21.7 1.0
16:15:00 −32:00:00 2022/01/06/08:41 21.6 1.0
16:15:30 −25:00:00 2022/01/09/08:37 21.2 1.9
16:13:30 −23:30:00 2022/01/09/08:38 20.8 2.2
16:11:00 −22:00:00 2022/01/09/08:39 20.9 2.1
16:12:00 −20:30:00 2022/01/09/08:44 20.4 2.0
16:10:00 −19:00:00 2022/01/09/08:45 20.5 1.8
22:43:00 −24:30:00 2022/01/13/00:58 21.3 1.2
16:33:30 −24:00:00 2022/01/13/08:47 21.5 0.9
16:31:30 −22:30:00 2022/01/13/08:48 21.6 0.9
16:30:00 −21:00:00 2022/01/13/08:49 21.5 0.9
16:29:00 −19:00:00 2022/01/13/08:53 21.3 0.9
16:28:00 −17:30:00 2022/01/13/08:54 21.2 0.9
16:43:16 −17:32:15 2022/01/18/08:49 21.1 1.4
23:20:00 −20:00:00 2022/01/21/00:49 21.3 1.3
23:23:30 −18:30:00 2022/01/21/00:50 21.4 1.3
23:27:00 −17:00:00 2022/01/21/00:51 21.5 1.3
23:30:30 −15:30:00 2022/01/21/00:52 21.5 1.3
16:55:15 −17:34:30 2022/01/21/08:50 21.5 1.2
17:03:00 −19:00:00 2022/01/21/08:51 21.5 1.2
17:06:00 −20:30:00 2022/01/21/08:52 21.4 1.2
17:12:00 −21:30:00 2022/01/21/08:57 21.2 1.2
17:15:00 −23:00:00 2022/01/21/08:58 21.1 1.2
17:02:00 −16:00:00 2022/01/22/08:52 21.2 1.5
16:59:30 −14:30:00 2022/01/22/08:53 21.2 1.5
16:57:30 −13:00:00 2022/01/22/08:54 21.2 1.5
17:03:40 −17:34:30 2022/01/23/08:55 21.8 1.1
16:57:00 −11:00:00 2022/01/23/08:57 21.8 1.1
17:14:30 −17:00:00 2022/01/24/08:54 21.4 1.3
16:59:50 −09:40:00 2022/01/24/08:55 21.4 1.3
16:59:00 −08:00:00 2022/01/24/08:58 21.2 1.3
8
The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
9. Volume Complete Cluster Survey (LoVoCCS; Dell’Antonio
2020; Fu et al. 2022) in collaboration with the DECam twilight
asteroid survey (Sheppard et al. 2021). The asteroid was
recovered the next night on August 14 at both the Baade–
Magellan telescope and again using DECam on the Blanco 4 m
telescope. As the object was relatively bright at 19.2 mag, it
could be tracked by 1 meter class telescopes. On August 15 the
asteroid was observed by DECam and Magellan as well as the
Las Cumbres 1 m telescopes in South Africa and Chile. It was
tracked with 1 m class telescopes for almost a month. In
addition, pre-discovery images of the asteroid were found from
DECam archival images on 2017 July 16, allowing the orbit to
be well determined. 2021 PH27 was also recovered again in
March 2022.
2021 PH27 has the smallest semimajor axis of any known
asteroid and thus the shortest orbital period for an asteroid of
about 113 days (Table 2). Only the planet Mercury has a
smaller known semimajor axis for any object in our solar
system. 2021 PH27 has an Atira-type asteroid orbit that always
keeps it inside of Earth’s orbit (Figure 7). Because 2021 PH27
has a fairly eccentric orbit, it crosses both the orbits of Mercury
and Venus and approaches the Sun to within about 0.133 au.
To understand the orbital behavior of 2021 PH27, we ran a
numerical orbital simulation using the SWIFT RMVS4
integrator described by Levison & Duncan (1994) and included
the planets Mercury, Venus, Earth+Moon (barycenter), Mars
(barycenter), Jupiter (barycenter), Saturn (barycenter), Uranus
(barycenter), and Neptune (barycenter). The time step of the
simulations was 0.1 days. We generated 1000 clones using the
JPL covariance matrix of 2021 PH27 from 2022 April 18. The
randomly generated points follow a six-dimensional normal
distribution defined by the covariance matrix and the orbital
elements as described by Namouni & Morais (2018).
The orbit of 2021 PH27 is dynamically unstable within a few
million year timescale (Figures 8 and 9). There is a 0.7%
chance that it will collide with Venus in the next million years,
and it will pass within Venus’ Hill sphere in the next 950 to
1050 yr, as all of our clones travel through Venus’ Hill sphere
Figure 5. The limiting magnitude of each twilight field vs. its elongation
distance from the Sun. Most of the fields had a limiting magnitude above 21
mag in the r band, with the best fields reaching nearly 22nd mag.
Figure 6. The moving object detection efficiency for the survey for a typical
field with 1 4 seeing. The typical field limiting magnitude was around 21.3
mag in the r band. Table 1 and Figure 5 shows the limiting magnitude of each
field of the DECam twilight survey.
Table 2
New Asteroid Discoveries
Name a e i H Diam Type
(au) (deg) (mag) (km)
2021 LJ4 0.676 0.382 9.827 20.1 0.3 − 0.6 Atira
2021 PH27 0.4617 0.712 31.927 17.7 0.9 − 1.7 Atira
2022 AP7 2.924 0.715 13.835 17.1 1.1 − 2.3 Apollo
Note. Orbital elements are from the Minor Planet Center as of 2022 June, with
the end number being the significant digit of the uncertainty. Though the
albedos are unknown, they are likely between 5% and 20% as many NEOs are
in this range (Pravec et al. 2012). Using the standard 14% albedo assumption
for unknown albedo NEOs, as used by the NASA Center for Near Earth Object
Studies, this means an absolute magnitude brighter than 17.75 mag is likely
larger than 1 km in size. The diameter range shown above is assuming 20% and
5% albedos, respectively.
Figure 7. The orbit of the newly discovered Atira asteroid 2021 PH27, which
has the smallest semimajor axis of any known asteroid. Though it orbits the Sun
faster than Venus as its semimajor axis is less than that of Venus, 2021 PH27
has an aphelion exterior to Venus. It also has a perihelion interior to Mercury’s
orbit, causing 2021 PH27 to experience the largest general relativistic effects
from the Sun’s gravity of any object known in the solar system.
9
The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
10. in that time. 2021 PH27ʼs very close perihelion to the Sun
means 2021 PH27 experiences the largest general relativistic
effects on any known object in our solar system, including
Mercury. We used the ReboundX code to determine the general
relativistic effects on 2021 PH27 from the Sun (Tamayo et al.
2020). The orbital precession rate of 2021 PH27 is about 53
arcseconds per century, which is faster than Mercury’s orbital
precession rate of about 43 arcseconds per century (Will 2018).
The general relativity effects are not important in 2021 PH27ʼs
orbital evolution as planetary perturbations are much more
significant. The asteroid interacts strongly with Venus and is
likely in some sort of Kozai–Lidov oscillation from Jupiter
and/or the inner planets as seen by the coupling of the
eccentricity and inclination of the evolution of 2021 PH27ʼs
orbit in Figure 9 (Kozai 1962; Lidov 1962; de la Fuente
Marcos & de la Fuente Marcos 2021). 2021 PH27ʼs orbit and
Venus overlap enough that it is a PHA to Venus with a Venus
Minimum Orbit Intersection Distance (MOID) of only 0.015. If
2021 PH27 is or becomes an active asteroid, it could create
meteor showers in Venus’ atmosphere (Albino et al. 2022).
2021 PH27 can reach surface temperatures of around 500°C
during its closest approach to the Sun. This means its surface
has been strongly thermally processed over time and its internal
structure likely has been heavily stressed from the intense and
changing thermal environment (Li & Jewitt 2013; Lisse &
Steckloff 2022).
2021 PH27 was relatively bright at discovery, being some
19.2 mag in the r band. As the aphelion distance is only
0.79 au, which is just beyond Venus’ orbit, this object, though
relatively bright and around 1 km in size, would be very hard
for most NEO surveys to find as they generally do not observe
near Venus’ orbit or interior to it. The large inclination of about
32° also means 2021 PH27 spends most of its time well away
from the ecliptic.
Though 2021 PH27 most likely came from the main asteroid
belt, it is possible that it could have originated much closer to
the Sun from a possible stable reservoir of small objects in
resonance with Venus or even the hypothetical Vulcanoid
population, which is a theoretical stable area of small bodies
interior to Mercury (Greenstreet et al. 2012).
3.2. 2021 LJ4: Atira Type
2021 LJ4 was found in twilight images taken on 2021 June 6
using DECam (Sheppard & Tholen 2021). The object was
recovered again using DECam on 2021 June 8 as well as on
2021 June 9 and 11 using the CFHT telescope on Maunakea.
Additional recoveries were later made using DECam. The
object was faint at 21.4 mag in the r band at discovery. The
asteroid appears to be a typical Atira type with a period of 0.55
yr and an aphelion just interior to Earth’s orbit at 0.93 au, with
it crossing the orbits of both Venus and Mercury (Table 2).
2021 LJ4 was recovered in 2021 November as well as 2022
Figure 8. The orbital stability of 2021 PH27 over a few thousand years. Each gray line shows one of the 1000 clone particles of 2021 PH27ʼs orbital parameters. The
bold middle yellow line shows the median orbital parameters of 2021 PH27 and the thin yellow lines the 1σ of the median value. The orbit is dynamically unstable and
2021 PH27 has numerous close encounters with Venus. The first close encounter with Venus occurs around the year 3000 AD (or 950–1050 yr from now or time
zero). This close encounter with Venus creates a noticable spread in the asteroid clones of 2021 PH27, as most of these clones get inside of Venus’ Hill sphere during
the encounter, modifying the orbit of 2021 PH27 depending on how close it gets to the planet.
10
The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
11. May, yielding a well-determined orbit for the object. Assuming
a moderate S-type asteroid albedo, the object is likely to be 300
to 400 m in diameter. Though 2021 LJ4 has only a moderate
inclination, its Atira orbit and somewhat small size make it hard
for most NEO surveys using smaller telescopes to detect this
asteroid, making it an ideal discovery using DECam during
twilight observing.
3.3. 2022 AP7: Apollo Type
The object 2022 AP7 was discovered using DECam in
twilight on 2022 January 13 (Sheppard 2022). It was recovered
using DECam a few nights later on 2022 January 16 using the
asteroid short-arc orbit and ephemeris computation program
(known as KNOBS) written by Tholen & Whiteley (2000).
Recovery occurred again using DECam on the nights of 2022
January 18, 21, and 23. After recovery a few weeks later using
the Las Cumbres telescopes and the University of Hawaii 88
inch telescope, 2022 AP7 was found in data from 2017 in both
the NEO Pan-STARRS and Catalina Sky Survey images, when
the object was last near opposition, though far from Earth and
thus faint. The orbit is thus very well known based on a ∼5
year observation arc. 2022 AP7 is an Apollo-type NEO which
crosses Earth’s orbit with a perihelion near 0.83 au and
aphelion near Jupiter at 5.0 au (Table 2).
The Earth MOID for 2022 AP7 is only 0.0475 au, making it
a PHA and likely the largest PHA found since 2014 based on
absolute magnitude. 2022 AP7 is likely to be in the top 5% of
the largest PHAs known. 2022 AP7 was relatively faint at
discovery being 20.8 mag, but because it was relatively far
from Earth at about 1.9 au and distant from the Sun around
1.4 au. It is a fairly large object, likely being well over 1 km in
size assuming a moderate albedo (1.0–2.3 km diameter for an
albedo of 0.25–0.05, respectively).
Such a large object with an orbital period of only 5 yr and
only a moderate inclination might be expected to have been
found earlier by one of the NEO surveys that cover most of the
sky exterior to Earth’s orbit. Thus either 2022 AP7 has an orbit
that aliases Earth’s orbit, keeping it usually at a large distance
from Earth when in the night sky near opposition, or 2022 AP7
may be brightening as it comes to perihelion from cometary
effects. 2022 AP7 was found as it approached perihelion,
which is when cometary activity is expected to increase
significantly. In our discovery and recovery images, no obvious
coma or tail was detected. As the orbital period of 2022 AP7 is
near exactly 5 yr, it does have an orbit that currently aliases
with Earth’s, keeping it well away from Earth when near
opposition for now, meaning it would only be efficiently found
in a twilight type survey as it would be near the Sun and
brightest only when Earth is more on the other side of the Sun
and its elongation very low. Thus 2022 AP7 is a discovery that
exemplifies how a relatively large telescope observing toward
the Sun during twilight can find large NEOs that most of the
current NEO surveys do not efficiently find. Many of the
“missing” yet-to-be-found ∼1 km sized NEOs likely have
orbits that alias with Earth, making them distant and faint when
in the night sky at opposition like 2022 AP7.
Figure 9. Same as Figure 8 but now showing the numerical orbital simulation of 2021 PH27 out to 100,000 yr. The orbit of 2021 PH27 is dynamically unstable over a
few million years with numerous close encounters with Venus. The coupling of the eccentricity and inclination over time suggests 2021 PH27 is experiencing a
resonant interaction with the planets.
11
The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
12. 4. Discussion
The main design of the survey was to find or put constraints
on the population and orbital properties of objects near to or
interior to Venus’ orbit. We did not find any relatively stable
Venus co-orbital or resonant objects, allowing us to put strong
upper limits on the size of such a population if it exists. Though
not the main goal of the survey, four Atira-type asteroids were
detected, which is ∼15% of the known Atira population. This
allows us to put significant constraints on the size of the Atira
population, which have orbits completely interior to Earth’s. In
addition, this survey is one of the few that can put modest
constraints on the Vatira population, which has orbits
completely interior to Venus’ orbit.
To determine what percentage of each interior population’s
orbits we may have surveyed, we performed several Monte
Carlo simulations. These simulations consisted of generating
100,000 clones of orbits of a particular population and then
determining how many of these objects our survey would have
been expected to detect based on the fields observed, limiting
magnitude of each field, and the efficiency of the survey. This
gives a rough percentage of the entire population of orbits. We
then use Poisson statistics to put limits or upper limits, in the
case of no detections, of each population simulated.
For each simulation we assumed asteroids of six spectral
types (S-type with 0.22 albedo, M with 0.17, E with 0.45, C
with 0.06, P with 0.04, and D with 0.05; Mainzer et al.
2011, 2012; Shevchenko et al. 2016; Morbidelli et al. 2020)
and three diameters (D = 0.5, 1.0, and 1.5 km) using the same
methods as detailed by Pokorny et al. (2020). See Pokorny
et al. (2020) for more details on our simulations, including the
phase function, apparent visual magnitude, and diameter
conversions we used in our simulations. The asteroid type
and hence the albedo of the asteroid only matters for detecting
objects less than 1 km as all objects, no matter their type, would
have similar detection efficiencies near or above 1 km as our
survey was deep enough to make almost all 1 km or bigger
inner asteroids efficiently detected.
4.1. Stable Venus Resonant Objects
Pokorny & Kuchner (2019) found that some low-eccen-
tricity, low-inclination Venus co-orbital objects could be in
resonance and stable for the age of the solar system. If this
population exists, it would be a very interesting population to
find and study as these objects could be the remnant of the
inner solar system’s formation disk. Pokorny et al. (2020)
performed a limited survey with DECam of the space near
Venus’ orbit to put modest constraints on this possible
population of stable Venus resonant co-orbitals. Here we
extend the Pokorny et al. (2020) analysis using the new, much
larger survey area covered near Venus’ orbit with DECam. For
this population we followed 100,000 clones of low-eccentri-
city, low-inclination Venus co-orbital asteroids that were
shown to be stable for the age of the solar system by Pokorny
& Kuchner (2019).
Based on our simulations, this DECam twilight survey
should have observed some 21%–23% of the entire population
of stable Venus co-orbitals larger than 1 km, which depends on
the spectral type and thus albedo of the objects (Table 3). Since
we found no relatively stable Venus resonant objects and there
are none known, this population is not likely to be very large.
We calculate the upper limit on the population size of 1 km or
larger stable Venus co-orbitals to be only about 4 3
6
-
+
, depending
on the asteroid type (Table 3). Similar constraints are found for
even smaller 0.5 km sized higher albedo asteroids types like the
S, M, and E types, as they would be relatively easier to find
because of their high reflectance. For the darker asteroid types,
like the C, P, and D types, smaller sized asteroids of 0.5 km are
basically unconstrained as most would be too faint for our
survey to detect efficiently (Table 3).
4.2. Unstable Venus Near Co-orbitals
There are five well observed asteroids that currently have
orbital periods similar to Venus: (322756) 2001 CK32,
(524522) 2002 VE68, 2012 XE133, 2013 ND15, and 2015
WZ12. All of these, as well as the newer objects found since
2020 are much smaller than 1 km and are on dynamically
unstable orbits on the order of a few million years, as discussed
in Section 1. We generated 100,000 clones using the above five
object’s semimajor axes, eccentricities, and inclinations by
randomly selecting the remaining orbital elements. Though we
did not observe any of these known objects, through this
simulation, we find our survey would have detected about 5%–
10% of the objects similar to these known dynamically
unstable Venus near co-orbitals and larger than 1 km in size,
depending on their albedos and spectral types (Table 4). From
this simulation there could be a few of these near unstable
Venus co-orbitals to discover around the 1 km size regime.
Table 3
Stable Venus Co-orbital Completeness Percentage and Population
Type D = 0.5 D = 1.0 D = 1.5
(km) (km) (km)
S-type 22%(4 3
6
-
+
) 23%(4 3
6
-
+
) 23%(4 3
6
-
+
)
M-Type 21%(4 3
7
-
+
) 23%(4 3
6
-
+
) 23%(4 3
6
-
+
)
E-Type 23%(4 3
6
-
+
) 23%(4 3
6
-
+
) 23%(4 3
6
-
+
)
C-Type 0.8%(100 80
170
-
+
) 21%(4 3
7
-
+
) 23%(4 3
6
-
+
)
P-Type 0.2%(540 400
900
-
+
) 20%(4 3
8
-
+
) 23%(4 3
6
-
+
)
D-Type 0.4%(210 150
350
-
+
) 21%(4 3
7
-
+
) 23%(4 3
6
-
+
)
Note. Survey completeness based on a Monte Carlo simulation of our survey
for each population in percent assuming the shown diameter (D) or larger and
asteroid type. In “()” is the computed upper limit on the population size based
on our survey coverage and null result.
Table 4
Unstable Venus Co-orbital Completeness Percentage and Population
Type D = 0.5 D = 1.0 D = 1.5
(km) (km) (km)
S-type 8%(10 7
16
-
+
) 10%(8 6
13
-
+
) 10%(8 6
13
-
+
)
M-Type 6%(12 9
20
-
+
) 10%(8 6
13
-
+
) 10%(8 6
13
-
+
)
E-Type 10%(8 6
13
-
+
) 10%(8 6
13
-
+
) 10%(8 6
13
-
+
)
C-Type 0.4%(220 170
360
-
+
) 7%(11 7
17
-
+
) 10%(8 6
13
-
+
)
P-Type 0.2%(440 330
720
-
+
) 5%(14 10
23
-
+
) 9%(8 6
13
-
+
)
D-Type 0.3%(310 230
510
-
+
) 7%(11 8
19
-
+
) 10%(8 6
13
-
+
)
Note. Survey completeness based on a Monte Carlo simulation of our survey
for each population in percent assuming the shown diameter or larger and
asteroid type. In “()” is the computed upper limit on the population size based
on our survey coverage and null result.
12
The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
13. 4.3. Atira/Apohele Asteroid Population
In addition to the two new Atira asteroids discovered in this
survey, 2021 LJ4 and 2021 PH27, we also detected
serendipitously the previously known Atira asteroids 2019
AQ3 and 2021 BS1. We used the semimajor axis, eccentricity,
and inclination of the 25 known Atira objects with well-
determined orbits as of 2022 March and randomly selected the
other orbital elements to generate 100,000 clones. Table 5
shows the percentage of the population of Atira objects our
survey should have detected, which amounts to 5%–8% of the
total population larger than 1 km, depending on the albedos of
the objects.
Our simulations show there are about 50 to 75 ± 35 Atiras
that are about 1 km or larger (Table 5), suggesting less than half
of the largest objects in the Atira population have been found to
date. Assuming there are about 1000 NEOs of 1 km or larger,
this would make the Atira population about 5% of the NEO
population. This result generally agrees with estimates of the
Atira population size from some earlier NEO models (Bottke
et al. 2002; Greenstreet et al. 2012), but is somewhat higher
than the currently modeled ∼1% for the Atira population
fraction of NEOs (Granvik et al. 2018).
These results are based on low number statistics and mostly
assumed albedos, so if the population size of 1 km Atira objects
is on the low end of the uncertainty, than there are likely only a
few large Atiras left to find. The larger undiscovered Atira
asteroids that remain probably have high inclinations and/or
smaller than average semimajor axes and/or eccentricities,
which would keep them mostly well interior to Earth’s orbit
and away from the darker skies where the main NEO surveys
operate most efficiently. This is true for the 1 km sized Atira
2021 PH27, which we found with a high inclination and very
low semimajor axis (Table 2).
4.4. Vatira Asteroid Population
Vatira asteroids have orbits completely interior to Venus’
orbit. Since the Vatira population’s orbital distribution is still
highly uncertain, we simulated two different Vatira populations
to understand how sensitive our survey would be to finding
Vatira asteroids. First, we used the semimajor axis, eccentricity,
and inclination of the only known Vatira asteroid (594913)
’Ayló’chaxnim (2020 AV2) and generated 100,000 clones by
randomly selecting the remaining orbital elements. In this
simulation, we would have found about 5% of the ∼1 km or
larger Vatira asteroids with similar orbits as 2020 AV2
(Table 6). This puts only minimal constraints on a Vatira
population with orbits like 2020 AV2, as there could still be tens
of objects like 2020 AV2 to be found since they spend most of
their time at smaller elongations than many of our survey fields.
In a second simulation, we made a 100,000 asteroid
hypothetical Vatira population by creating a somewhat circular
and moderately inclined population through randomly selecting
orbital elements with 0.50 < a < 0.60 au, 0.0 < e < 0.1, and
0 < i < 15° and randomly selecting the other remaining orbital
elements between 0 and 360°. As many of the objects in this
hypothetical Vatira population would not have elongations as
great as 2020 AV2, it would be much harder to detect these
objects in our fields. Thus our survey would only find at most
about 1% of objects in this hypothetical Vatira population
(Table 7).
5. Conclusions and Summary
The twilight survey using DECam on the CTIO Blanco 4 m
telescope is one of the largest area and sensitive searches ever
performed for objects interior to Earth’s and near Venus’ orbit.
Though no objects with orbits similar to or interior to Venus’
orbit were found, the survey did find three relatively large
NEOs, including two Atira and one Apollo orbital type. The
new discovery 2021 PH27 is about 1 km in size and has the
smallest semimajor axis and thus shortest orbital period around
the Sun of any known asteroid. 2021 PH27 has strong
interactions with Venus, with it likely passing through Venus’
Hill sphere in 950–1050 yr from now, making it a PHA to
Venus. The eccentric orbit of 2021 PH27 means it crosses both
Mercury’s and Venus’ orbit and its very low perihelion of only
Table 5
Atira/Apohele Asteroid Population Completeness Percentage and Population
Type D = 0.5 D = 1.0 D = 1.5
(km) (km) (km)
S-type 7%(55 ± 30) 8%(50 ± 25) 8%(50 ± 25)
M-Type 6%(65 ± 35) 8%(50 ± 25) 8%(50 ± 25)
E-Type 8%(50 ± 25) 8%(50 ± 25) 8%(50 ± 25)
C-Type 0.4%(950 ± 500) 7%(60 ± 30) 8%(50 ± 25)
P-Type 0.3%(1500 ± 800) 6%(75 ± 35) 8%(50 ± 25)
D-Type 0.3%(1200 ± 600) 6%(65 ± 30) 8%(50 ± 25)
Note. Survey completeness based on a Monte Carlo simulation of our survey
for each population in percent assuming the shown diameter (D) or larger and
asteroid type. In “()” is the computed upper limit on the population size based
on our survey coverage and finding four Atira asteroids within the survey.
Table 6
Vatira Asteroids like 2020 AV2 Population Completeness Percentage
Type D = 0.5 D = 1.0 D = 1.5
(km) (km) (km)
S-type 5%(17 13
30
-
+
) 5%(16 12
30
-
+
) 5%(16 12
30
-
+
)
M-Type 5%(19 15
30
-
+
) 5%(16 12
30
-
+
) 5%(16 12
30
-
+
)
E-Type 5%(16 12
30
-
+
) 5%(16 12
30
-
+
) 5%(16 12
30
-
+
)
C-Type 0.7%(130 100
220
-
+
) 5%(18 14
30
-
+
) 5%(16 12
30
-
+
)
P-Type 0.5%(170 130
270
-
+
) 5%(19 15
30
-
+
) 5%(16 12
30
-
+
)
D-Type 0.5%(160 120
270
-
+
) 5%(19 15
30
-
+
) 5%(16 12
30
-
+
)
Note. Survey completeness based on a Monte Carlo simulation of our survey
for each population in percent assuming the shown diameter (D) or larger and
asteroid type. In “()” is the computed upper limit on the population size based
on our survey coverage and null result.
Table 7
Circular Vatira Asteroid Population Completeness Percentage
Type D = 0.5 D = 1.0 D = 1.5
(km) (km) (km)
S-type 1% 1% 1%
M-Type 1% 1% 1%
E-Type 1% 1% 1%
C-Type 0.3% 0.9% 1%
P-Type 0.3% 0.9% 1%
D-Type 0.3% 0.9% 1%
Note. Survey completeness based on a Monte Carlo simulation of our survey
for each population in percent assuming the shown diameter (D) or larger and
asteroid type.
13
The Astronomical Journal, 164:168 (15pp), 2022 October Sheppard et al.
14. 0.13 au creates about a 53 arcsecond per century precession in
its orbit from general relativistic effects, which are the largest
known in our solar system. The newly discovered 2022 AP7 is
an Apollo-type NEO that is probably the largest potentially
hazardous NEO to Earth found in several years, being some 1.5
km in size. There are likely several more 1 km sized Atira-type
asteroids left to find, which probably have low semimajor axes
and high inclinations, like 2021 PH27, making them hard to
find for most asteroid surveys. The DECam twilight survey is
covering sky geometries and areas that most other surveys do
not cover to depths not usually obtained, filling an important
niche in the survey for the last few remaining relatively large
unknown NEOs. Interestingly, the twilight survey has
discovered more larger asteroids (1 km) than smaller ones
even though the survey is sensitive to smaller asteroids. This
might suggest the smaller asteroids are dynamically less stable
and/or more susceptible to break-up from the extreme thermal
and gravitational environment near the Sun, though additonal
discoveries of asteriods with orbits near the Sun must be made
to determine statistically if the smaller asteroids are under-
abundant since in general they are also harder to detect.
Observations were obtained at Cerro-Tololo Inter-American
Observatory, National Optical Astronomy Observatory, which
are operated by the Association of Universities for Research in
Astronomy, under contract with the National Science Founda-
tion. This project used data obtained with the Dark Energy
Camera (DECam), which was constructed by the Dark Energy
Survey (DES) collaborating institutions: Argonne National
Lab, University of California Santa Cruz, University of
Cambridge, Centro de Investigaciones Energeticas, Medioam-
bientales y Tecnologicas-Madrid, University of Chicago,
University College London, DES-Brazil consortium, Univer-
sity of Edinburgh, ETH-Zurich, University of Illinois at
Urbana-Champaign, Institut de Ciencies de l’Espai, Institut
de Fisica d’Altes Energies, Lawrence Berkeley National Lab,
Ludwig-Maximilians Universitat, University of Michigan,
National Optical Astronomy Observatory, University of
Nottingham, Ohio State University, University of Pennsylva-
nia, University of Portsmouth, SLAC National Lab, Stanford
University, University of Sussex, and Texas A&M University.
Funding for DES, including DECam, has been provided by the
U.S. Department of Energy, National Science Foundation,
Ministry of Education and Science (Spain), Science and
Technology Facilities Council (UK), Higher Education Fund-
ing Council (England), National Center for Supercomputing
Applications, Kavli Institute for Cosmological Physics, Finan-
ciadora de Estudos e Projetos, Fundação Carlos Chagas Filho
de Amparo a Pesquisa, Conselho Nacional de Desenvolvi-
mento Científico e Tecnológico and the Ministério da Ciência e
Tecnologia (Brazil), the German Research Foundation-spon-
sored cluster of excellence “Origin and Structure of the
Universe” and the DES collaborating institutions. D.T. was
supported by NASA grant 80NSSC21K0807. P.P. was
supported by NASA ISFM EIMM award, the NASA
Cooperative Agreement 80GSFC21M0002 and NASA solar
system Workings award 80NSSC21K0153. T.S.R. acknowl-
edges funding from the NEO-MAPP project (H2020-EU-2-1-
6/870377). C.M. was partially supported by the international
Gemini Observatory, a program of NSFʼs NOIRLab, which is
managed by the Association of Universities for Research in
Astronomy (AURA) under a cooperative agreement with the
National Science Foundation, on behalf of the Gemini
partnership of Argentina, Brazil, Canada, Chile, the Republic
of Korea, and the United States of America. This work was
(partially) funded by the Spanish MICIN/AEI/10.13039/
501100011033 and by “ERDF A way of making Europe” by
the “European Union” through grant RTI2018-095076-B-C21,
and the Institute of Cosmos Sciences University of Barcelona
(ICCUB, Unidad de Excelencia María de Maeztu’) through
grant CEX2019-000918-M. This work makes use of observa-
tions from the Las Cumbres Observatory global telescope
network. This paper includes data gathered with the 6.5 m
Magellan Telescopes located at Las Campanas Observatory,
Chile.
ORCID iDs
Scott S. Sheppard https:/
/orcid.org/0000-0003-3145-8682
David J. Tholen https:/
/orcid.org/0000-0003-0773-1888
Petr Pokorný https:/
/orcid.org/0000-0002-5667-9337
Marco Micheli https:/
/orcid.org/0000-0001-7895-8209
Ian Dell’Antonio https:/
/orcid.org/0000-0003-0751-7312
Shenming Fu https:/
/orcid.org/0000-0001-5422-1958
Chadwick A. Trujillo https:/
/orcid.org/0000-0001-
9859-0894
Rachael Beaton https:/
/orcid.org/0000-0002-1691-8217
Scott Carlsten https:/
/orcid.org/0000-0002-5382-2898
Alex Drlica-Wagner https:/
/orcid.org/0000-0001-8251-933X
Clara Martínez-Vázquez https:/
/orcid.org/0000-0002-
9144-7726
Sidney Mau https:/
/orcid.org/0000-0003-3519-4004
Toni Santana-Ros https:/
/orcid.org/0000-0002-0143-9440
Luidhy Santana-Silva https:/
/orcid.org/0000-0003-
3402-6164
Cristóbal Sifón https:/
/orcid.org/0000-0002-8149-1352
Sunil Simha https:/
/orcid.org/0000-0003-3801-1496
Audrey Thirouin https:/
/orcid.org/0000-0002-1506-4248
David Trilling https:/
/orcid.org/0000-0003-4580-3790
A. Katherina Vivas https:/
/orcid.org/0000-0003-4341-6172
Alfredo Zenteno https:/
/orcid.org/0000-0001-6455-9135
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