Discovery of a_probable_4_5_jupiter_mass_exoplanet_to_hd95086_by_direct_imagingSérgio Sacani
The document reports the discovery of a probable 4-5 Jupiter-mass exoplanet orbiting the young star HD 95086. Deep imaging observations using VLT/NaCo detected a faint source at a separation of 56 AU from the star. Follow-up observations over more than a year found the source to be co-moving with the star, suggesting it is bound. Its luminosity corresponds to a predicted mass of 4-5 Jupiter masses, making it the lowest mass exoplanet directly imaged around a star. If confirmed, this discovery could provide insights into giant planet formation and evolution.
The APACHE Project is a long-term photometric survey aimed at discovering transiting exoplanets around hundreds of nearby M dwarf stars using an array of 400-mm telescopes. The project has conducted a pilot study and is now carrying out its long-term survey. It has already discovered several new variable stars and eclipsing binary systems. The survey works closely with other programs like GAPS and will benefit from precise Gaia parallax measurements of target stars.
Uma espetacular colisão de galáxias foi descoberta além da Via Láctea. O sistema mais próximo já descoberto, a identificação foi anunciada por uma equipe de astrônomos liderada pelo Professor Quentin Parker da Universidade de Hong Kong e pelo Professor Albert Zijlstra na Universidade de Manchester.
A galáxia está a 30 milhões de anos-luz de distância, o que significa que ela é relativamente próxima. Ela foi chamada de Roda de Kathryn, em homenagem à sua semelhança com o famoso fogo de artifício e também em homenagem à esposa do coautor do trabalho.
Esses sistemas são muito raros e nascem da colisão entre duas galáxias de tamanhos similares. As ondas de choque geradas na colisão comprimem o reservatório de gás em cada galáxia e disparam a formação de novas estrelas. Isso cria um espetacular anel de intensa emissão, e ilumina o sistema, do mesmo modo que a Roda Catherine ilumina a noite num show de fogos de artifício.
As galáxias crescem através de colisões, mas é raro registrar esse processo acontecendo, e é extremamente raro ver o anel da colisão em progresso. Pouco mais de 20 sistemas com anéis completos são conhecidos.
Observational evidence from supernovae for an accelerating universe and a cos...Sérgio Sacani
The document presents observations of 10 type Ia supernovae (SNe Ia) with redshifts between 0.16 and 0.62. Combined with previous data from the team and others, the distances to the 16 high-redshift SNe Ia are on average 10-15% farther than expected in a low-mass density universe without a cosmological constant. Different analysis methods find evidence favoring an expanding universe with a positive cosmological constant and acceleration of the expansion. The data are consistent with an accelerating universe and cosmological constant at a statistical significance of 2.8-9 sigma depending on the method and assumptions.
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
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.
Evidence for a_distant_giant_planet_in_the_solar_systemSérgio Sacani
A descoberta de um novo planeta, atualmente não é uma manchete que chama tanto assim a atenção das pessoas. Muito disso, graças ao Telescópio Espacial Kepler, que já descobriu quase 2000 exoplanetas e todo instante uma nova descoberta é anunciada, certo? Mais ou menos, a descoberta anunciada hoje, dia 20 de Janeiro de 2016, é um pouco diferente, pois não se trata de um exoplaneta, e sim de um novo planeta no Sistema Solar, e esse é um fato que intriga os astrônomos a muitos e muitos anos.
Porém, temos que ir com calma com esses anúncios. No artigo aceito para publicação no The Astronomical Journal (artigo no final do post), os autores, Mike Brown e Konstantin Batygin, do Instituto de Tecnologia da Califórnia, apresentaram o que eles dizem ser evidências circunstâncias fortes para a existência de um grande planeta ainda não descoberto, talvez, com uma massa 10 vezes a massa da Terra, orbitando os confins do nosso Sistema Solar, muito além da órbita de Plutão. Os cientistas inferiram sua presença, por meio de anomalias encontradas nas órbitas de seis objetos do chamado Cinturão de Kuiper.
O objeto, que os pesquisadores estão chamando de Planeta Nove, não chega muito perto do Sol, no ponto mais próximo da sua órbita ele fica a 30.5 bilhões de quilômetros, ou seja, cinco vezes a distância entre o Sol e Plutão. Apesar do seu grande tamanho, ele é muito apagado, e por isso ninguém até o momento conseguiu observá-lo.
Não existe ainda uma confirmação observacional da descoberta, mas as evidências são tão fortes que fizeram com que outros especialistas como Chad Trujilo do Observatório Gemini no Havaí e David Nesvorny, do Southwest Research Institute em Boulder no Colorado, ficassem impressionados e bem convencidos de que deve mesmo haver um grande planeta nas fronteiras da nossa vizinhança cósmica.
Discovery of a_probable_4_5_jupiter_mass_exoplanet_to_hd95086_by_direct_imagingSérgio Sacani
The document reports the discovery of a probable 4-5 Jupiter-mass exoplanet orbiting the young star HD 95086. Deep imaging observations using VLT/NaCo detected a faint source at a separation of 56 AU from the star. Follow-up observations over more than a year found the source to be co-moving with the star, suggesting it is bound. Its luminosity corresponds to a predicted mass of 4-5 Jupiter masses, making it the lowest mass exoplanet directly imaged around a star. If confirmed, this discovery could provide insights into giant planet formation and evolution.
The APACHE Project is a long-term photometric survey aimed at discovering transiting exoplanets around hundreds of nearby M dwarf stars using an array of 400-mm telescopes. The project has conducted a pilot study and is now carrying out its long-term survey. It has already discovered several new variable stars and eclipsing binary systems. The survey works closely with other programs like GAPS and will benefit from precise Gaia parallax measurements of target stars.
Uma espetacular colisão de galáxias foi descoberta além da Via Láctea. O sistema mais próximo já descoberto, a identificação foi anunciada por uma equipe de astrônomos liderada pelo Professor Quentin Parker da Universidade de Hong Kong e pelo Professor Albert Zijlstra na Universidade de Manchester.
A galáxia está a 30 milhões de anos-luz de distância, o que significa que ela é relativamente próxima. Ela foi chamada de Roda de Kathryn, em homenagem à sua semelhança com o famoso fogo de artifício e também em homenagem à esposa do coautor do trabalho.
Esses sistemas são muito raros e nascem da colisão entre duas galáxias de tamanhos similares. As ondas de choque geradas na colisão comprimem o reservatório de gás em cada galáxia e disparam a formação de novas estrelas. Isso cria um espetacular anel de intensa emissão, e ilumina o sistema, do mesmo modo que a Roda Catherine ilumina a noite num show de fogos de artifício.
As galáxias crescem através de colisões, mas é raro registrar esse processo acontecendo, e é extremamente raro ver o anel da colisão em progresso. Pouco mais de 20 sistemas com anéis completos são conhecidos.
Observational evidence from supernovae for an accelerating universe and a cos...Sérgio Sacani
The document presents observations of 10 type Ia supernovae (SNe Ia) with redshifts between 0.16 and 0.62. Combined with previous data from the team and others, the distances to the 16 high-redshift SNe Ia are on average 10-15% farther than expected in a low-mass density universe without a cosmological constant. Different analysis methods find evidence favoring an expanding universe with a positive cosmological constant and acceleration of the expansion. The data are consistent with an accelerating universe and cosmological constant at a statistical significance of 2.8-9 sigma depending on the method and assumptions.
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
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.
Evidence for a_distant_giant_planet_in_the_solar_systemSérgio Sacani
A descoberta de um novo planeta, atualmente não é uma manchete que chama tanto assim a atenção das pessoas. Muito disso, graças ao Telescópio Espacial Kepler, que já descobriu quase 2000 exoplanetas e todo instante uma nova descoberta é anunciada, certo? Mais ou menos, a descoberta anunciada hoje, dia 20 de Janeiro de 2016, é um pouco diferente, pois não se trata de um exoplaneta, e sim de um novo planeta no Sistema Solar, e esse é um fato que intriga os astrônomos a muitos e muitos anos.
Porém, temos que ir com calma com esses anúncios. No artigo aceito para publicação no The Astronomical Journal (artigo no final do post), os autores, Mike Brown e Konstantin Batygin, do Instituto de Tecnologia da Califórnia, apresentaram o que eles dizem ser evidências circunstâncias fortes para a existência de um grande planeta ainda não descoberto, talvez, com uma massa 10 vezes a massa da Terra, orbitando os confins do nosso Sistema Solar, muito além da órbita de Plutão. Os cientistas inferiram sua presença, por meio de anomalias encontradas nas órbitas de seis objetos do chamado Cinturão de Kuiper.
O objeto, que os pesquisadores estão chamando de Planeta Nove, não chega muito perto do Sol, no ponto mais próximo da sua órbita ele fica a 30.5 bilhões de quilômetros, ou seja, cinco vezes a distância entre o Sol e Plutão. Apesar do seu grande tamanho, ele é muito apagado, e por isso ninguém até o momento conseguiu observá-lo.
Não existe ainda uma confirmação observacional da descoberta, mas as evidências são tão fortes que fizeram com que outros especialistas como Chad Trujilo do Observatório Gemini no Havaí e David Nesvorny, do Southwest Research Institute em Boulder no Colorado, ficassem impressionados e bem convencidos de que deve mesmo haver um grande planeta nas fronteiras da nossa vizinhança cósmica.
A nearby yoiung_m_dwarf_with_wide_possibly_planetary_m_ass_companionSérgio Sacani
This document summarizes the identification of two young objects, TYC 9486-927-1 and 2MASS J21265040−8140293, as a likely very wide binary system. It presents revised astrometry showing they have common proper motion. Spectroscopy of the secondary yields a radial velocity consistent with the primary. Analysis of lithium absorption and kinematics suggests an age range of 10-45 Myr, with the secondary having an estimated mass in the planetary mass regime. If confirmed, this would be the widest known exoplanet system at over 4500 AU separation.
Probing the innermost_regions_of_agn_jets_and_their_magnetic_fields_with_radi...Sérgio Sacani
Desde 1974, observações feitas com o chamado Long Baseline Interferometry, ou VLBI, combinaram sinais de um objeto cósmico recebidos em diferentes rádio telescópios espalhados pelo globo para criar uma antena com o tamanho equivalente à maior separação entre elas. Isso fez com que fosse possível fazer imagens com uma nitidez sem precedentes, com uma resolução 1000 vezes melhor do que Hubble consegue na luz visível. Agora, uma equipe internacional de astrônomos quebrou todos os recordes combinando 15 rádio telescópios na Terra e a antena de rádio da missão RadioAstron, da agência espacial russa, na órbita da Terra. O trabalho, liderado pelo Instituto de Astrofísica de Andalucía, o IAA-CSIC, forneceu novas ideias sobre a natureza das galáxias ativas, onde um buraco negro extremamente massivo engole a matéria ao redor enquanto simultaneamente emite um par de jatos de partículas de alta energia e campos magnéticos a velocidades próximas da velocidade da luz.
Observações feitas no comprimento de onda das micro-ondas são essenciais para explorar esses jatos, já que os elétrons de alta energia se movendo em campos magnéticos são mais proficientes em produzir micro-ondas. Mas a maioria das galáxias ativas com jatos brilhantes estão a bilhões de anos-luz de distância da Terra, de modo que esses jatos são minúsculos no céu. Desse modo a alta resolução é essencial para observar esses jatos em ação e então revelar fenômenos como as ondas de choque e a turbulência que controla o quanto de luz é produzida num dado tempo. “Combinando pela primeira vez rádio telescópios na Terra com rádio telescópios no espaço, operando na máxima resolução, tem permitido que a nossa equipe crie uma antena que tem um tamanho equivalente a 8 vezes o diâmetro da Terra, correspondendo a 20 micro arcos de segundo”, disse José L; Gómez, o líder da equipe no Instituto de Astrofísica de Andalucía, IAA-CSIC.
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
This document summarizes a blind HI survey of the southern Milky Way zone of avoidance conducted with the Parkes radio telescope. The survey detected 883 galaxies at Galactic longitudes 212° < l < 36° and latitudes |b| < 5° to a sensitivity of 6 mJy per 27 km/s channel. Fifty-one percent of detections had known optical/near-infrared counterparts, while 27% had new counterparts identified. The survey delineated large-scale structures in the Puppis and Great Attractor regions for the first time. Several newly identified galaxy concentrations and clusters were revealed that help trace the Great Attractor Wall.
Uma grande equipe de astrônomos registrou uma supernova extremamente luminosa numa galáxia massiva a cerca de 3.82 bilhões de anos-luz de distância.
A explosão recém-descoberta, denominada de ASASSN-15Ih, pertence à classe mais luminosa de supernovas, chamada de supernovas superluminosas.
"Ela parece ter originado numa grande galáxia, em contraste com a maioria das supernovas superluminosas, que normalmente se originam em galáxias anãs com formação de estrelas", disse o Dr. Subo Dong, do Kavli Institute for Astronomy and Astrophysics e coautor do artigo publicado na revista Science que descreve a descoberta.
"Nós estimamos o raio efetivo para a galáxia de 7830 anos-luz e uma massa estelar de 200 bilhões de massas solares".
Também conhecida como SN 2015L, a ASASSN-15lh é aproximadamente 200 vezes mais poderosa do que uma típica explosão de supernova do Tipo Ia, cerca de 570 bilhões de vezes mais brilhante do que o nosso Sol, e vinte vezes mais brilhante do que todas as estrelas na nossa galáxia combinadas.
This document provides a summary of Annalisa Calamida's background and experience. She is currently a postdoctoral research associate at the National Optical Astronomy Observatory studying faint white dwarfs with Hubble Space Telescope images. Her research interests include globular clusters, the Galactic bulge, stellar evolution, and variable stars. She has extensive experience reducing imaging and spectroscopic data as well as simulating observations for future telescopes. Calamida has authored or co-authored over 15 refereed publications on topics related to globular clusters and the Galactic bulge.
Stellar-like objects with effective temperatures of 2700K and below are referred to as
20 "ultracool dwarfs"1. This heterogeneous group includes both extremely low-mass stars
21 and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion),
22 and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on
23 the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for
24 ultracool dwarfs predicts a large, but heretofore undetected, population of close-in
25 terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable
26 volatile-rich Earth-sized planets7. Here we report the discovery of three short-period
27 Earth-sized planets transiting an ultracool dwarf star 12 parsecs away. The inner two
28 planets receive four and two times the irradiation of Earth, respectively, placing them
29 close to the inner edge of the habitable zone of the star8. Eleven orbits remain possible
30 for the third planet based on our data, the most likely resulting in an irradiation
31 significantly smaller than Earth's. The infrared brightness of the host star combined
32 with its Jupiter-like size offer the possibility of constraining the composition and
33 thoroughly characterizing the atmospheric properties of the components of this nearby
34 planetary system, notably to detect potential biosignatures.
The identification of_93_day_periodic_photometric_variability_for_yso_ylw_16aSérgio Sacani
This study identifies a 93 day periodic photometric variability in the Class I young stellar object (YSO) YLW 16A in the Rho Ophiuchus star forming region. Light curve analysis reveals variations of ~0.5 magnitudes in the Ks band over this period. The authors propose a triple system model consisting of an inner binary with a 93 day period eclipsed by a warped circumbinary disk, with a tertiary companion at ~40 AU responsible for warping the disk. This model is similar to one previously proposed for another YSO, WL 4, and may indicate such triple systems with eclipsing disks are common around young stars. Understanding these systems can provide insights into stellar and planetary formation and evolution.
Visible spectra of (474640) 2004 VN112–2013 RF98 with OSIRIS at the 10.4 m GT...Sérgio Sacani
The existence of significant anisotropies in the distributions of the directions of perihelia and
orbital poles of the known extreme trans-Neptunian objects (ETNOs) has been used to claim
that trans-Plutonian planets may exist. Among the known ETNOs, the pair (474640) 2004
VN112–2013 RF98 stands out. Their orbital poles and the directions of their perihelia and their
velocities at perihelion/aphelion are separated by a few degrees, but orbital similarity does
not necessarily imply common physical origin. In an attempt to unravel their physical nature,
visible spectroscopy of both targets was obtained using the OSIRIS camera-spectrograph at the
10.4 m Gran Telescopio Canarias (GTC). From the spectral analysis, we find that 474640–2013
RF98 have similar spectral slopes (12 versus 15 per cent/0.1 µm), very different from Sedna’s
but compatible with those of (148209) 2000 CR105 and 2012 VP113. These five ETNOs belong
to the group of seven linked to the Planet Nine hypothesis. A dynamical pathway consistent
with these findings is dissociation of a binary asteroid during a close encounter with a planet
and we confirm its plausibility using N-body simulations. We thus conclude that both the
dynamical and spectroscopic properties of 474640–2013 RF98 favour a genetic link and their
current orbits suggest that the pair was kicked by a perturber near aphelion
A estrela KIC 8462852 voltou a ser comentada na mídia astronômica essa semana, e vamos entender porque. Mas antes uma pequena recordação.
Provavelmente, você já ouviu falar da estrela KIC 8462852, que recebeu o nome carinhoso de Estrela de Tabby, em homenagem a Tabetha Boyajian que liderou a equipe que descobriu o seu estranho comportamento. Essa foi a estrela que chamou muito a atenção da imprensa no final do último ano. Os astrônomos utilizaram observações feitas com o Kepler e mediram as variações no brilho da estrela. Algumas dessas variações eram significativas, com uma queda de brilho de cerca de 20%.
Isso é muito. Não poderia ser um planeta passando em frente a estrela, pois as quedas dos brilhos também não eram periódicas, e a quantidade de luz bloqueada era diferente a cada vez. Além disso, até um planeta do tamanho de Júpiter, bloqueia menos de 1% da luz da estrela.
No artigo original, Boyajian e sua equipe discutiu uma série de hipóteses e possíveis cenários que poderiam causar a queda de brilho, eliminando algumas delas e levantando outras. Entre as hipóteses, aquela que ganhou uma força foi a de uma família de cometas passando na frente da estrela, com alguns deles colidindo entre si e gerando uma nuvem espessa que poderia bloquear a luz da estrela.
This document discusses a study that used difference imaging techniques to search for variable stars and microlensing events in the elliptical galaxy Centaurus A. The study obtained deep photometric data over almost two months using the Wide Field Imager on the ESO/MPG 2.2 m telescope. It detected 271 variable stars in Centaurus A with a detection limit of magnitude 24.5. Based on a simple model of Centaurus A's halo, the study estimated it could detect around 4 microlensing events per year, but a higher sensitivity is needed for a meaningful microlensing survey. The spatial distribution of any microlensing events could help constrain the shape of Centaurus A's dark matter halo.
The nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
This document summarizes the analysis of periodic variable stars in the open cluster NGC 3766 based on a 7-year monitoring campaign. The authors detected a new class of 36 variable stars located between the instability strips for slowly pulsating B stars and delta Scuti stars, where no variability was previously predicted. The majority of these new variables have periods between 0.1-0.7 days and amplitudes of 1-4 millimagnitudes. The properties of this new class are discussed and the authors argue they are likely pulsating variables sustained by stellar rotation. Additionally, the authors identify other periodic variables such as eclipsing binaries, slowly pulsating B stars, delta Scuti stars, and gamma Doradus candidates.
Artigo descreve a descoberta de um sistema de anéis 200 vezes maior do que o sistema de anéis de Saturno num exoplaneta orbitando a jovem estrela J1407
Chiotelis Ioannis, Theodoropoulou Maria, “Searching for Black Holes. Photometry in our Classrooms”, Hellenic Conference on Innovating STEM Education, 16-18 December 2016, Athens, Greece.
Small scatter and_nearly_isothermal_mass_profiles_to_four_half_light_radii_fr...Sérgio Sacani
This document summarizes the results of a study analyzing the total mass density profiles of 14 early-type galaxies using two-dimensional stellar kinematic data out to large radii of 2-6 half-light radii. The study finds that the total density profiles are well described by a nearly-isothermal power law with density proportional to radius from 0.1 to at least 4 half-light radii. The average logarithmic slope is -2.19 with a small scatter of only 0.11. This places tight constraints on galaxy formation models and illustrates the power of extended two-dimensional stellar kinematic observations.
The Evolution of Elliptical Galaxies in Rich ClustersRobert Berrington
This document summarizes research on the properties of early-type galaxies in rich galaxy clusters. It finds that rich clusters contain thousands of galaxies and have masses of around 1015 solar masses, while poor clusters contain hundreds of galaxies with masses of around 1014 solar masses. The physics of cluster mergers is driven by gravitational forces, with the total gravitational energy available during a merger calculated based on the masses and velocities of the merging clusters. Mergers can create shocks that accelerate particles and produce radio halos and relics detectable by radio and gamma-ray observatories. The properties of the Coma Cluster, a likely ongoing three-body merger, are modeled to study nonthermal particle acceleration and radiation from the merger.
Chaos Theory, PowerPoints, and Cartography: From Presentations to Career Plan...Safelink Internet Services
Designed for an English Major class on internships, job hunting, career planning, and ethical codes. I introduce the course using the math and physics area of chaos theory. The intent is to illustrate possibilities in presentations, key issues to be addressed in the course, and the chaos theory approach to career planning. Professionals now that career and life paths are anything but linear. I emphasize to students that this is fine, that chaos does not necessarily mean an absence of order, and that each life event and choice affects the trajectory of their future experiences.
A nearby yoiung_m_dwarf_with_wide_possibly_planetary_m_ass_companionSérgio Sacani
This document summarizes the identification of two young objects, TYC 9486-927-1 and 2MASS J21265040−8140293, as a likely very wide binary system. It presents revised astrometry showing they have common proper motion. Spectroscopy of the secondary yields a radial velocity consistent with the primary. Analysis of lithium absorption and kinematics suggests an age range of 10-45 Myr, with the secondary having an estimated mass in the planetary mass regime. If confirmed, this would be the widest known exoplanet system at over 4500 AU separation.
Probing the innermost_regions_of_agn_jets_and_their_magnetic_fields_with_radi...Sérgio Sacani
Desde 1974, observações feitas com o chamado Long Baseline Interferometry, ou VLBI, combinaram sinais de um objeto cósmico recebidos em diferentes rádio telescópios espalhados pelo globo para criar uma antena com o tamanho equivalente à maior separação entre elas. Isso fez com que fosse possível fazer imagens com uma nitidez sem precedentes, com uma resolução 1000 vezes melhor do que Hubble consegue na luz visível. Agora, uma equipe internacional de astrônomos quebrou todos os recordes combinando 15 rádio telescópios na Terra e a antena de rádio da missão RadioAstron, da agência espacial russa, na órbita da Terra. O trabalho, liderado pelo Instituto de Astrofísica de Andalucía, o IAA-CSIC, forneceu novas ideias sobre a natureza das galáxias ativas, onde um buraco negro extremamente massivo engole a matéria ao redor enquanto simultaneamente emite um par de jatos de partículas de alta energia e campos magnéticos a velocidades próximas da velocidade da luz.
Observações feitas no comprimento de onda das micro-ondas são essenciais para explorar esses jatos, já que os elétrons de alta energia se movendo em campos magnéticos são mais proficientes em produzir micro-ondas. Mas a maioria das galáxias ativas com jatos brilhantes estão a bilhões de anos-luz de distância da Terra, de modo que esses jatos são minúsculos no céu. Desse modo a alta resolução é essencial para observar esses jatos em ação e então revelar fenômenos como as ondas de choque e a turbulência que controla o quanto de luz é produzida num dado tempo. “Combinando pela primeira vez rádio telescópios na Terra com rádio telescópios no espaço, operando na máxima resolução, tem permitido que a nossa equipe crie uma antena que tem um tamanho equivalente a 8 vezes o diâmetro da Terra, correspondendo a 20 micro arcos de segundo”, disse José L; Gómez, o líder da equipe no Instituto de Astrofísica de Andalucía, IAA-CSIC.
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
This document summarizes a blind HI survey of the southern Milky Way zone of avoidance conducted with the Parkes radio telescope. The survey detected 883 galaxies at Galactic longitudes 212° < l < 36° and latitudes |b| < 5° to a sensitivity of 6 mJy per 27 km/s channel. Fifty-one percent of detections had known optical/near-infrared counterparts, while 27% had new counterparts identified. The survey delineated large-scale structures in the Puppis and Great Attractor regions for the first time. Several newly identified galaxy concentrations and clusters were revealed that help trace the Great Attractor Wall.
Uma grande equipe de astrônomos registrou uma supernova extremamente luminosa numa galáxia massiva a cerca de 3.82 bilhões de anos-luz de distância.
A explosão recém-descoberta, denominada de ASASSN-15Ih, pertence à classe mais luminosa de supernovas, chamada de supernovas superluminosas.
"Ela parece ter originado numa grande galáxia, em contraste com a maioria das supernovas superluminosas, que normalmente se originam em galáxias anãs com formação de estrelas", disse o Dr. Subo Dong, do Kavli Institute for Astronomy and Astrophysics e coautor do artigo publicado na revista Science que descreve a descoberta.
"Nós estimamos o raio efetivo para a galáxia de 7830 anos-luz e uma massa estelar de 200 bilhões de massas solares".
Também conhecida como SN 2015L, a ASASSN-15lh é aproximadamente 200 vezes mais poderosa do que uma típica explosão de supernova do Tipo Ia, cerca de 570 bilhões de vezes mais brilhante do que o nosso Sol, e vinte vezes mais brilhante do que todas as estrelas na nossa galáxia combinadas.
This document provides a summary of Annalisa Calamida's background and experience. She is currently a postdoctoral research associate at the National Optical Astronomy Observatory studying faint white dwarfs with Hubble Space Telescope images. Her research interests include globular clusters, the Galactic bulge, stellar evolution, and variable stars. She has extensive experience reducing imaging and spectroscopic data as well as simulating observations for future telescopes. Calamida has authored or co-authored over 15 refereed publications on topics related to globular clusters and the Galactic bulge.
Stellar-like objects with effective temperatures of 2700K and below are referred to as
20 "ultracool dwarfs"1. This heterogeneous group includes both extremely low-mass stars
21 and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion),
22 and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on
23 the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for
24 ultracool dwarfs predicts a large, but heretofore undetected, population of close-in
25 terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable
26 volatile-rich Earth-sized planets7. Here we report the discovery of three short-period
27 Earth-sized planets transiting an ultracool dwarf star 12 parsecs away. The inner two
28 planets receive four and two times the irradiation of Earth, respectively, placing them
29 close to the inner edge of the habitable zone of the star8. Eleven orbits remain possible
30 for the third planet based on our data, the most likely resulting in an irradiation
31 significantly smaller than Earth's. The infrared brightness of the host star combined
32 with its Jupiter-like size offer the possibility of constraining the composition and
33 thoroughly characterizing the atmospheric properties of the components of this nearby
34 planetary system, notably to detect potential biosignatures.
The identification of_93_day_periodic_photometric_variability_for_yso_ylw_16aSérgio Sacani
This study identifies a 93 day periodic photometric variability in the Class I young stellar object (YSO) YLW 16A in the Rho Ophiuchus star forming region. Light curve analysis reveals variations of ~0.5 magnitudes in the Ks band over this period. The authors propose a triple system model consisting of an inner binary with a 93 day period eclipsed by a warped circumbinary disk, with a tertiary companion at ~40 AU responsible for warping the disk. This model is similar to one previously proposed for another YSO, WL 4, and may indicate such triple systems with eclipsing disks are common around young stars. Understanding these systems can provide insights into stellar and planetary formation and evolution.
Visible spectra of (474640) 2004 VN112–2013 RF98 with OSIRIS at the 10.4 m GT...Sérgio Sacani
The existence of significant anisotropies in the distributions of the directions of perihelia and
orbital poles of the known extreme trans-Neptunian objects (ETNOs) has been used to claim
that trans-Plutonian planets may exist. Among the known ETNOs, the pair (474640) 2004
VN112–2013 RF98 stands out. Their orbital poles and the directions of their perihelia and their
velocities at perihelion/aphelion are separated by a few degrees, but orbital similarity does
not necessarily imply common physical origin. In an attempt to unravel their physical nature,
visible spectroscopy of both targets was obtained using the OSIRIS camera-spectrograph at the
10.4 m Gran Telescopio Canarias (GTC). From the spectral analysis, we find that 474640–2013
RF98 have similar spectral slopes (12 versus 15 per cent/0.1 µm), very different from Sedna’s
but compatible with those of (148209) 2000 CR105 and 2012 VP113. These five ETNOs belong
to the group of seven linked to the Planet Nine hypothesis. A dynamical pathway consistent
with these findings is dissociation of a binary asteroid during a close encounter with a planet
and we confirm its plausibility using N-body simulations. We thus conclude that both the
dynamical and spectroscopic properties of 474640–2013 RF98 favour a genetic link and their
current orbits suggest that the pair was kicked by a perturber near aphelion
A estrela KIC 8462852 voltou a ser comentada na mídia astronômica essa semana, e vamos entender porque. Mas antes uma pequena recordação.
Provavelmente, você já ouviu falar da estrela KIC 8462852, que recebeu o nome carinhoso de Estrela de Tabby, em homenagem a Tabetha Boyajian que liderou a equipe que descobriu o seu estranho comportamento. Essa foi a estrela que chamou muito a atenção da imprensa no final do último ano. Os astrônomos utilizaram observações feitas com o Kepler e mediram as variações no brilho da estrela. Algumas dessas variações eram significativas, com uma queda de brilho de cerca de 20%.
Isso é muito. Não poderia ser um planeta passando em frente a estrela, pois as quedas dos brilhos também não eram periódicas, e a quantidade de luz bloqueada era diferente a cada vez. Além disso, até um planeta do tamanho de Júpiter, bloqueia menos de 1% da luz da estrela.
No artigo original, Boyajian e sua equipe discutiu uma série de hipóteses e possíveis cenários que poderiam causar a queda de brilho, eliminando algumas delas e levantando outras. Entre as hipóteses, aquela que ganhou uma força foi a de uma família de cometas passando na frente da estrela, com alguns deles colidindo entre si e gerando uma nuvem espessa que poderia bloquear a luz da estrela.
This document discusses a study that used difference imaging techniques to search for variable stars and microlensing events in the elliptical galaxy Centaurus A. The study obtained deep photometric data over almost two months using the Wide Field Imager on the ESO/MPG 2.2 m telescope. It detected 271 variable stars in Centaurus A with a detection limit of magnitude 24.5. Based on a simple model of Centaurus A's halo, the study estimated it could detect around 4 microlensing events per year, but a higher sensitivity is needed for a meaningful microlensing survey. The spatial distribution of any microlensing events could help constrain the shape of Centaurus A's dark matter halo.
The nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
This document summarizes the analysis of periodic variable stars in the open cluster NGC 3766 based on a 7-year monitoring campaign. The authors detected a new class of 36 variable stars located between the instability strips for slowly pulsating B stars and delta Scuti stars, where no variability was previously predicted. The majority of these new variables have periods between 0.1-0.7 days and amplitudes of 1-4 millimagnitudes. The properties of this new class are discussed and the authors argue they are likely pulsating variables sustained by stellar rotation. Additionally, the authors identify other periodic variables such as eclipsing binaries, slowly pulsating B stars, delta Scuti stars, and gamma Doradus candidates.
Artigo descreve a descoberta de um sistema de anéis 200 vezes maior do que o sistema de anéis de Saturno num exoplaneta orbitando a jovem estrela J1407
Chiotelis Ioannis, Theodoropoulou Maria, “Searching for Black Holes. Photometry in our Classrooms”, Hellenic Conference on Innovating STEM Education, 16-18 December 2016, Athens, Greece.
Small scatter and_nearly_isothermal_mass_profiles_to_four_half_light_radii_fr...Sérgio Sacani
This document summarizes the results of a study analyzing the total mass density profiles of 14 early-type galaxies using two-dimensional stellar kinematic data out to large radii of 2-6 half-light radii. The study finds that the total density profiles are well described by a nearly-isothermal power law with density proportional to radius from 0.1 to at least 4 half-light radii. The average logarithmic slope is -2.19 with a small scatter of only 0.11. This places tight constraints on galaxy formation models and illustrates the power of extended two-dimensional stellar kinematic observations.
The Evolution of Elliptical Galaxies in Rich ClustersRobert Berrington
This document summarizes research on the properties of early-type galaxies in rich galaxy clusters. It finds that rich clusters contain thousands of galaxies and have masses of around 1015 solar masses, while poor clusters contain hundreds of galaxies with masses of around 1014 solar masses. The physics of cluster mergers is driven by gravitational forces, with the total gravitational energy available during a merger calculated based on the masses and velocities of the merging clusters. Mergers can create shocks that accelerate particles and produce radio halos and relics detectable by radio and gamma-ray observatories. The properties of the Coma Cluster, a likely ongoing three-body merger, are modeled to study nonthermal particle acceleration and radiation from the merger.
Chaos Theory, PowerPoints, and Cartography: From Presentations to Career Plan...Safelink Internet Services
Designed for an English Major class on internships, job hunting, career planning, and ethical codes. I introduce the course using the math and physics area of chaos theory. The intent is to illustrate possibilities in presentations, key issues to be addressed in the course, and the chaos theory approach to career planning. Professionals now that career and life paths are anything but linear. I emphasize to students that this is fine, that chaos does not necessarily mean an absence of order, and that each life event and choice affects the trajectory of their future experiences.
This document discusses systems and chaos theory. It explains that complex adaptive systems like ant colonies, organizations, and markets are made up of interacting agents that self-organize through evolving rules and a dynamic environment. While such systems can exist in states of stasis or chaos with shifting patterns, order can still emerge from their complex and unpredictable behaviors. The document provides sources on chaos theory and systems theory and how they apply to understanding cities, ecosystems, and other complex systems.
The document discusses chaos theory and Lorenz attractors. It defines key terms like chaos, attractors, and strange attractors. It then summarizes Edward Lorenz's work developing the Lorenz attractor using a system of three differential equations with three variables (x, y, z) and constants (σ, ρ, β) to model atmospheric convection. The Lorenz attractor exhibits sensitive dependence on initial conditions, known as the "butterfly effect". Though initially developed for weather, the Lorenz equations have since been applied to other areas exhibiting chaotic behavior.
Chaos Theory And Strategy: Theory Application And Managerial ImplicationsTaimur Khan
The document discusses applying chaos theory to strategic management. It argues that industries evolve dynamically over time due to complex interactions between actors, making them difficult to predict and model with traditional linear theories. Chaos theory provides a useful framework for understanding non-linear industrial systems as chaotic and complex. While long-term planning is challenging, chaos theory allows for short-term forecasting due to patterns. The document also presents a supply chain model to demonstrate how chaos theory can help managers address uncertainty and disruption over time.
This document provides an overview of chaos theory and some key concepts within it. It defines chaos as a dynamic process where new patterns emerge from pieces coming together, rather than a dissolution of patterns. Chaos theory models nonlinear and complex behaviors in systems. Key constructs of chaos theory discussed include strange attractors, basins of attraction, fractals, bifurcation, unpredictability, self-organization, and spontaneity. The document emphasizes that chaos represents an opportunity for change and new patterns rather than violence or disruption.
Chaos theory proposes that seemingly random events may actually arise from deterministic systems and can be predicted. It views organizations as complex systems with nonlinear relationships between variables. Applying chaos theory to organizational crises suggests that: 1) small changes can have large effects; 2) long-term predictions are impossible but short-term are feasible; 3) crises may arise from bifurcation points where outcomes oscillate. Chaos theory provides an alternative lens for analyzing unpredictable crisis events in organizations.
The document discusses complex adaptive systems and chaos theory. It notes that complex adaptive systems consist of interacting agents that self-organize and their dynamic interactions can result in emergent behaviors. Their behaviors may seem unpredictable as patterns can appear and disappear suddenly, but there is still an underlying order that is difficult to describe simply. Chaos theory also describes systems that are deterministic but unpredictable in practice, following rules but appearing random in their evolution over time. Punctuated equilibrium and bifurcations are discussed as features of systems at the "edge of chaos".
This presentation discusses chaos theory and the butterfly effect. It begins with an introduction that defines the butterfly effect as how small variations can dramatically change the outcome of a system over time. There are three types of systems: linear, random, and chaotic, which are deterministic yet unpredictable long-term.
The history section describes how meteorologist Edward Lorenz discovered the butterfly effect in 1961 when a small variation in input data led to vastly different weather model outputs. The term "butterfly effect" comes from a 1972 quote about whether a butterfly could cause a tornado.
Applications of chaos theory discussed include weather prediction, stock markets, biology, physics, evolution, fractals, aviation safety, traffic patterns, psychology, and time travel
Chaos theory is a mathematical field of study which states that non-linear dynamical systems
that are seemingly random are actually deterministic from much simpler equations. The
phenomenon of Chaos theory was introduced to the modern world by Edward Lorenz in 1972
with conceptualization of ‘Butterfly Effect’. As chaos theory was developed by inputs of
various mathematicians and scientists, it found applications in a large number of scientific
fields.
The purpose of the project is the interpretation of chaos theory which is not as familiar as
other theories. Everything in the universe is in some way or the other under control of Chaos
or product of Chaos. Every motion, behavior or tendency can be explained by Chaos Theory.
The prime objective of it is the illustration of Chaos Theory and Chaotic behavior.
This project includes origin, history, fields of application, real life application and limitations
of Chaos Theory. It explores understanding complexity and dynamics of Chaos.
This document provides a brief introduction and discussion of chaos theory. It begins by emphasizing the importance of empiricism in gaining knowledge from nature. Chaos theory introduces disorder and confusion that can arise from certainty. The document then discusses how chaos theory is highly technical but is beginning to take off in behavioral sciences. It poses questions about chaos theory's potential and pitfalls for scientific theory and observation. The rest of the document aims to provide an introduction to key chaos theory concepts while balancing conceptual and rigorous presentations, and discusses applications in psychology and comparisons to other scientific trends.
Chaos theory describes the behavior of complex nonlinear systems that are highly sensitive to initial conditions and undergo unpredictable changes. Some key aspects include strong dependence on initial conditions, no long-term predictability despite being deterministic, and the presence of strange attractors where the system evolves towards yet never repeats. Chaos can be observed in population dynamics models where fluctuating growth rates lead to unpredictable oscillations or jumps between population values. Controlling chaos involves perturbing a chaotic system to stabilize it towards a desired periodic behavior.
The document provides an overview of chaos theory, including its key characteristics and history. It discusses Edward Lorenz's discovery of the butterfly effect using a simplified weather model. Lorenz found that small changes to initial conditions could drastically alter long-term outcomes, making predictions impossible. This led to the concept of sensitive dependence on initial conditions in chaotic systems. The document also describes Lorenz's water wheel experiment and the Lorenz attractor diagram that helped establish chaos theory.
The document discusses several historical periods and events that acted as attractors or influences on knowledge and society, including:
1) The Renaissance period saw a focus on life rather than just the afterlife and attracted Greek scholars to Italy following the fall of Constantinople.
2) The Scientific Revolution and Age of Enlightenment brought new discoveries and ways of thinking that paved the way for later developments.
3) The Industrial Revolution was influenced by population growth, migration to cities, demand for factories, and inventions like the steam engine that created large labor workforces and increased trade to sustain large populations.
This document provides an overview of chaos theory, including:
1) It defines chaos as the apparently noisy, aperiodic behavior in deterministic systems that is sensitive to initial conditions.
2) Important milestones in chaos theory research are discussed, from Poincare in 1890 to fractal geometry work in the 1970s.
3) Attractors, strange attractors, and fractal geometry are introduced as important concepts.
4) Methods for measuring chaos like Lyapunov exponents and entropy are described.
American Astronomical Society plenary talkMichael Norman
This document discusses 20 years of computational progress in simulating the first generation of galaxies, or protogalaxies, that formed after the Big Bang. It describes how powerful supercomputers and open-source software tools have allowed researchers to simulate the formation and properties of these early galaxies through detailed modeling of the relevant physics. Key findings include that the first galaxies formed around 100 million years after the Big Bang, were massive, and provided enough ionizing photons to help reionize the universe by redshift 7, resolving discrepancies with observational data. The simulations have significantly advanced understanding of galaxy formation from the first stars to the earliest galaxy populations.
Gwendolyn Eadie: A New Method for Time Series Analysis in Astronomy with an A...JeremyHeyl
1. The document describes a new method called Multitaper + Lomb-Scargle (MTLS) for estimating the power spectrum of unevenly sampled time series data, such as that from astronomical observations.
2. MTLS combines the Multitaper method, which reduces spectral leakage and variance, with the Lomb-Scargle method, which can handle uneven sampling times.
3. The document provides an example application of MTLS to estimate the power spectrum of a red giant star using Kepler telescope lightcurve data, finding an improvement over the standard Lomb-Scargle method.
This document discusses several topics related to cosmology and the search for extraterrestrial life, including:
1) Dimensionless numbers and ratios in physics and cosmology like the fine structure constant and ratios involving cosmological and atomic quantities.
2) Estimates of the number of atoms in the observable universe and other cosmological values.
3) The Drake equation and Fermi paradox regarding the search for extraterrestrial intelligence.
4) Coincidences between values that seem finely-tuned to allow for life like nuclear resonance energies.
Advanced space propulsion concepts for interstellar travelMarcus 2012
When a particle and its antiparticle collide, they annihilate each other and are converted to energy according to Einstein's mass-energy equivalence formula E=mc2. Three concepts for utilizing this are:
1) Magnetic confinement fusion uses magnetic fields to contain a plasma and fuse atomic nuclei for propulsion.
2) Gas-core nuclear fission contains fission fuel in a high-temperature plasma for propulsion, but magnetic containment is challenging.
3) Matter-antimatter annihilation could provide the highest energy density, but generating and containing significant amounts of antimatter poses major technical hurdles.
From Darkness, Light: Computing Cosmological ReionizationCosmoAIMS Bassett
1) Reionization occurred between redshifts of 10-6, beginning around 10 billion years ago and ending around 1 billion years ago.
2) Observations of the CMB and galaxies at z>6 provide constraints but questions remain about the sources and topology of reionization.
3) Cosmological simulations of reionization must model structure formation, radiation transport, and non-equilibrium chemistry and physics to help address open questions.
A rock composition_for_earth_sized_exoplanetsSérgio Sacani
1) Researchers measured the mass of Kepler-78b, an Earth-sized exoplanet orbiting its host star every 8.5 hours, to be 1.69 ± 0.41 M⊕ using Doppler spectroscopy of the star's radial velocity variations.
2) Given the planet's radius of 1.20 ± 0.09 R⊕, its mean density of 5.3 ± 1.8 g/cm3 is similar to Earth's, suggesting a rocky composition of iron and rock.
3) Kepler-78b is the smallest exoplanet yet characterized with both an accurate mass and radius measurement, extending measurements of planetary composition into the size range of Earth and Venus.
Measurement of Jupiter’s asymmetric gravity fieldSérgio Sacani
The gravity harmonics of a fluid, rotating planet can be decomposed
into static components arising from solid-body rotation and dynamic
components arising from flows. In the absence of internal dynamics,
the gravity field is axially and hemispherically symmetric and is
dominated by even zonal gravity harmonics J2n that are approximately
proportional to qn, where q is the ratio between centrifugal
acceleration and gravity at the planet’s equator1
. Any asymmetry in the
gravity field is attributed to differential rotation and deep atmospheric
flows. The odd harmonics, J3, J5, J7, J9 and higher, are a measure of the
depth of the winds in the different zones of the atmosphere2,3
. Here
we report measurements of Jupiter’s gravity harmonics (both even
and odd) through precise Doppler tracking of the Juno spacecraft
in its polar orbit around Jupiter. We find a north–south asymmetry,
which is a signature of atmospheric and interior flows. Analysis of
the harmonics, described in two accompanying papers4,5
, provides
the vertical profile of the winds and precise constraints for the depth
of Jupiter’s dynamical atmosphere.
Eccentricity from transit_photometry_small_planets_in_kepler_multi_planet_sys...Sérgio Sacani
Artigo descreve estudo que mostra que a órbita dos exoplanetas terrestres são na sua maioria órbitas circulares, o que é bom para se procurar por vida e o que vem causando uma revolução no entendimento sobre os sistemas de exoplanteas.
This document discusses three key questions in cosmology: dark matter, inflation, and dark energy. It provides evidence for dark matter from early observations of galaxy rotation curves and clusters. It also summarizes modern evidence from Planck for the matter content of the universe. Regarding inflation, it discusses the generic predictions and open questions about the inflaton field. For dark energy, it reviews evidence from supernovae and Planck and discusses theoretical challenges like the fine-tuning and coincidence problems. It also outlines proposed and ongoing experiments to better understand dark matter, inflation, and dark energy.
Studies of ngc_6720_with_calibrated_hst_wfc3_emission_line_filter_imagesSérgio Sacani
This study uses calibrated Hubble Space Telescope images of the Ring Nebula (NGC 6720) taken 12.925 years apart to measure tangential motions within the nebula. Individual features were measured in nitrogen emission line images as well as dark knots seen against oxygen emission. The results indicate that the nebula is expanding homologously, but at a faster rate along its major axis. Dark knots were found to expand more slowly than the nebular gas. The tangential motion measurements allow estimates of the nebula's distance and dynamic age to be about 720 pc and 4000 years, respectively.
An earth sized_planet_with_an_earth_sized_densitySérgio Sacani
1) Researchers observed the exoplanet Kepler-78b using the HARPS-N spectrograph to measure its mass.
2) They measured Kepler-78b's mass to be 1.86 Earth masses, giving it a density similar to Earth, implying a rocky composition of iron and rock.
3) The small size of Kepler-78b makes it the smallest exoplanet yet measured for both mass and radius, establishing that Earth-sized planets can be terrestrial.
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
This document reports the discovery of a newly discovered optical Einstein ring (ER) called the "Canarias Einstein Ring". It was discovered serendipitously in imaging data from the Dark Energy Camera. Follow-up spectroscopy with the Gran Telescopio CANARIAS confirmed the nature of the system, with the lens being an early-type galaxy at a redshift of z=0.581 and the source being a starburst galaxy at z=1.165. Analysis of the system determined the Einstein radius to be 2.16 arcseconds and the total enclosed mass producing the lensing effect to be 1.86 ± 0.23 × 1012 solar masses.
Kepler-62 is a star with five planets detected via the Kepler spacecraft, including two super-Earth planets in the star's habitable zone (HZ). The outermost planets, Kepler-62e and Kepler-62f, are 1.61 and 1.41 Earth radii respectively and receive fluxes of 1.2 and 0.41 times that of Earth. Theoretical models suggest these planets could be solid, with rocky or water compositions. Kepler-62e and Kepler-62f are the smallest planets detected by Kepler to orbit in another star's HZ.
Third epoch magellanic_clouud_proper_motionsSérgio Sacani
The document analyzes proper motion data from the Hubble Space Telescope to study the three-dimensional rotation field of the Large Magellanic Cloud (LMC) galaxy. It finds that:
1) The proper motion data implies a stellar dynamical center that coincides with the HI dynamical center from previous studies.
2) Combining the proper motion and line-of-sight velocity data provides insights into the LMC's rotation curve, disk viewing angles, and circular rotation speed of 91.7 km/s outside the central region.
3) The data paint a consistent picture of LMC rotation and yield improved constraints on the galaxy's distance, mass profile, and orbital history around the Milky Way.
The energy falling on a 1 m^2 surface on Earth in a year is:
Lsun x π x 1 x (1 year) = 3.90x1026 W x π x 1 x (3600 s/hr x 24 hr/day x 365.25 day/year) = 1.36x1017 J
Where Lsun is the luminosity of the Sun (3.90x1026 W) and 1 year is converted to seconds.
This document provides an introduction to the course on stellar structure and evolution. It defines a star as an object that radiates energy from an internal source and is bound by its own gravity. Observational constraints on stellar properties include photometry, spectroscopy, interferometry and binary star analysis. The Hertzsprung-Russell diagram reveals correlations between luminosity and effective temperature that must be explained. Mass-luminosity and mass-radius relations from eclipsing binaries show tight correlations between these properties. Stars are divided into populations based on their location, age and metallicity.
The mass of_the_mars_sized_exoplanet_kepler_138_b_from_transit_timingSérgio Sacani
Artigo da revista Nature, descreve o trabalho de astrônomos para medir o tamanho e a massa de um exoplaneta parecido com Marte, além de caracterizar por completo o sistema planetário da estrela Kepler-138.
This document summarizes an 8-year survey using the HARPS spectrograph to detect super-Earth and Neptune-mass planets around solar-type stars. Over 50% of solar-type stars were found to harbor at least one planet within 100 days. The mass distribution of super-Earths and Neptune-mass planets increases sharply from 30-15 Earth masses. Most of these planets belong to multi-planetary systems and have orbital eccentricities under 0.45. In contrast, giant planets are more common around metal-rich stars and can have eccentricities over 0.9. The precision of HARPS enables detection of planets in the habitable zones of solar-type stars.
Similar to N4.Lemaitre - "Stability of an asteroid satellite" (20)
N.28 di martino-impact-and-non-impact-craters-in-eastern-sahIAPS
The document describes a crater field in the Eastern Sahara that was previously thought to be impact craters but was found through field work and analysis to actually be formed by endogenous processes related to volcanic activity. It also describes two circular structures in Libya called the Arkenu craters that were determined to likely be formed by subvolcanic intrusions and hydrothermal alteration, not meteorite impacts. Additionally, it summarizes the discovery of a new giant impact crater found in Egypt's western desert through satellite image analysis.
Reimagining Your Library Space: How to Increase the Vibes in Your Library No ...Diana Rendina
Librarians are leading the way in creating future-ready citizens – now we need to update our spaces to match. In this session, attendees will get inspiration for transforming their library spaces. You’ll learn how to survey students and patrons, create a focus group, and use design thinking to brainstorm ideas for your space. We’ll discuss budget friendly ways to change your space as well as how to find funding. No matter where you’re at, you’ll find ideas for reimagining your space in this session.
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptxEduSkills OECD
Iván Bornacelly, Policy Analyst at the OECD Centre for Skills, OECD, presents at the webinar 'Tackling job market gaps with a skills-first approach' on 12 June 2024
How to Make a Field Mandatory in Odoo 17Celine George
In Odoo, making a field required can be done through both Python code and XML views. When you set the required attribute to True in Python code, it makes the field required across all views where it's used. Conversely, when you set the required attribute in XML views, it makes the field required only in the context of that particular view.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
Your Skill Boost Masterclass: Strategies for Effective Upskilling
N4.Lemaitre - "Stability of an asteroid satellite"
1. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Stability of an asteroid satellite
Anne Lemaître, Audrey Compère, Nicolas Delsate
Department of Mathematics FUNDP Namur
14 June 2010
2. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
1 Introduction
2 Satellites of asteroids
System Ida-Dactyl
Previous results
3 Stability tests
Numerical simulations
Classical calculation of the potential
MacMillan potential
Chaos indicator : MEGNO
4 Chaos Maps
Gravitational resonances
Frequency analysis
5 Analytical development
MacMillan potential
Approximated formulation
1:1 resonance
Equatorial resonant orbits
Polar resonant orbits
6 Conclusions
3. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Motivation
Previous studies : rotation of the planets and natural satellites
and space debris on geostationary orbits
Collaboration Grasse - CNES : stability conditions for the
motion of a probe around an asteroid
To test our methods on asteroid satellites (PhD - not
published)
Stability : numerical tests and dynamical models
Several approaches of the potential of a non spherical body
Trace-free tensors in elliptical harmonics
Geometrical approach
MacMillan potential : the only one presented here (Paolo)
4. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Vocabulary
Binary asteroid : system of two asteroids
Two categories :
1 The two bodies have the same size : double asteroid
Ex : Antiope - Dynamics intensively studied in particular by Scheeres and
collaborators
2 A body is much smaller than the other one : asteroid and its satellite
Ex : Ida-Dactyl
5. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Natural system Ida-Dactyl
Ida : main belt asteroid (Koronis family), very irregular shape and fast spin
Ida Dactyl
Mass (4.2 ± 0.6) × 1016 kg ∼ 4.1012 kg
Diameter 59.8 × 25.4 × 18.6 km 1.6 × 1.4 × 1.2 km
6. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Dactyl :
Orbit data :
Semimajor axis (a) : 108 km
Orbital period (P) : 1.54 days
Eccentricity (e) : ≥ 0.2?
Other data :
Mean radius : 0.7 km
Principal diameters : 1.6 × 1.4 × 1.2 km
Shape : less irregular then Ida
Ellisoidal t (radii) : 0,8 × 0,7 × 0,6 km
Mass : ∼ 4.1012 kg
Surface area : 6,3 km2
Volume : 1,4 km3
Spin period : 8 hr
7. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Ida-Dactyl simulations
J-M Petit et al : 1998, Belton, 1996
Context :
Ida mass is not known precisely.
Each value of the mass corresponds to a Keplerian orbit for Dactyl
To constraint the mass of Ida by Dactyl's orbit
Belton,1996
8. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Petit et al
1. Stability bounds on Ida mass
First model
Ida is represented by an ellipsoid.
Gravitational potential : elliptic integrals
Integrator : Bulirsch and Stoer with a precision of 10−10
Masses : between 3.65 × 1016 and 5.7 × 1016 kg
Results :
Orbits with M 4.93 × 1016 kg (q 63 km) are very unstable.
→ crash or escape after several hours or days
The other orbits are stable for hundreds of years.
Second model
Approximation of Ida by a collection of 44 spheres of dierent sizes.
⇒ more precise bounds.
9. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Resonant stable orbits
The Ida-Dactyl system should be stable for long time ⇒ search for resonances
between the rotation of Ida and the orbital frequency of Dactyl.
Simulations results :
Most probable resonances 5:1 and 9:2
10. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Numerical simulations
Model : a point mass orbiting an ellipsoid
Parameters : shape, mass and spin of the primary, initial
conditions of the satellite
Purpose : search for stable or resonant systems
Technique : chaos maps (MEGNO)
Software : NIMASTEP (N. Delsate) written for numerical
integration of an articial satellite around a telluric planet
Dierences : irregular shape and fast rotation of the primary,
large eccentricity of the satellite, relative importance of the
perturbations
11. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
First calculation of the potential
Based on the spherical harmonics as for the telluric planets
Small deformations of a sphere
n
GM ∞
Re n
V (r , θ, λ) = 1+ Pnm (sin θ) (Cnm cos mλ + Snm sin mλ)
r n=2 m=0
r
(r , θ, λ) are the spherical coordinates
Re is the equatorial radius
Pnm are the Legendre's polynomials
Cnm et Snm are the spherical harmonics coecients
12. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Check of the integrations
Paper of A. Rossi, F. Marzari and P. Farinella (1999) : Orbital
evolution around irregular bodies in Earth, Planets, Space.
Four approaches of the potential :
Ivory's approach : direct calculation of the potential of an
homogeneous triaxial ellipsoid
Spherical harmonics approach (4th order)
Mascons approach : the body is approximated by a set of
point masses placed in a suitable place to reproduce the mass
distribution
Polyhedral approach : the body is approximated by a
polyhedron with a great number of faces
Axisymmetric ellipsoid (a = b = 10 km, c= 5 km) or triaxial
ellipsoid (a=30 km, b=10 km and c = 6.66 km).
13. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Tests of Rossi, Marzari and Farinella
Four cases :
Case 0 : Sphere (not considered here)
Case 1 : Axisymmetric ellipsoid with inclined circular orbits
(i = 10◦ ) at a distance of 20km - 5835 mascons - 1521 faces -
Mass = 2.0831015 kg - ρ = 1g cm3 .
Case 2 : Axisymmetric ellipsoid with inclined elliptic orbits
(e = 0.2)
Case 3 : Axisymmetric ellipsoid with distant inclined elliptic
orbits at a distance of 40km
14. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Comparisons
First tests : Variation of the ascending node (in radians s
−1 ) :
Secular Theory (J2 ) polygones mascons spherical harmonics
Case 1
circular inclined -7.7 10−6 -1.09 10−5 -1.11 10−5 -1.07 10−5
Case 2
elliptic inclined -8.37 10−6 -1.25 10−5 -1.33 10−5 -1.27 10−5
Case 3
elliptic, inclined and distant -7.10 10−7 -7.76 10−7 -7.92 10−7 -7.85 10−7
15. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
MacMillan potential
New potential : Potential for an ellipsoid : MacMillan (1958)
V (x , y , z ) = 3 GM
+∞
x2 y2 z2 ds
Z „ «
1− − − √ √
2 λ1 s2 s 2 − h2 s2 − k2 s 2 − h2 s 2 − k 2
where
h
2
= a2 − b2 et k 2 = a2 − c 2 (a, b et c are the semi-major
axes of the ellipsoid with a ≥ b ≥ c )
(x , y , z ) are the cartesian coordinates of the point
λ1 is the rst ellipsoidal coordinate of the point
16. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
For each (x , y , z ) :
x
2 y
2 z
2
+ 2 + 2 =1 Equation of degree 3 in s 2
s2 s − h2 s − k2
Roots : λ2 , λ2 et λ2 with 0 ≤ λ2 ≤ h2 ≤ λ2 ≤ k 2 ≤ λ2 .
1 2 3 3 2 1
Geometrically (x , y , z ) is the intersection between
an ellipsoid with axes ( λ2 , λ2 − h2 ,
1 1 λ2 − k 2 )
1
an hyperboloid of one sheet with axes
( λ2 ,
2 λ2 − h2 ,
2 k2 − λ2 )
2
an hyperboloid of two sheets with axes
( λ2 ,
3 h2 − λ2 ,
3 k2 − λ2 )
3
Ellipsoidal coordinates : (λ1 , λ2 , λ3 )
17. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
New tests and comparisons with Rossi et al
Calculation of the force components explicitly (partial
derivatives)
Gauss-Legendre quadrature for the integrals
Introduction in NIMASTEP
New tests : Variation of the ascending node (in radians s
−1 ) :
Secular Theory (J2 ) polygones mascons spherical harmonics Mac Millan
Case 1 -7.7 10−6 -1.09 10−5 -1.11 10−5 -1.07 10−5 -1.11 10−5
−6 −5 −5 −5
Case 2 -8.37 10 -1.25 10 -1.33 10 -1.27 10 -1.33 10−5
Case 3 -7.10 10−7 -7.76 10−7 -7.92 10−7 -7.85 10−7 -7.86 10−7
18. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Orbits
19. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Tests on the system Ida-Dactyl
Test on eccentric Dactyl orbits :
Resultats :
Crash or escapes for M ≥ 5 × 1016 kg
Regular orbits for M ≤ 5 × 1016 kg
⇒ same results as Petit et al. (1998)
20. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Chaos indicator : MEGNO
MEGNO = Mean Exponential Growth factor of Nearby Orbits
(Cincotta et Simo, 2000)
Dynamical system : : dt x (t ) = f (x (t )), x ∈ IR2n .
d
φ(t ) a solution function of time t
δφ (t ) the tangent vector along φ(t ) with δ˙φ = ∂ x (φ(t ))δφ (t ).
∂f
The MEGNO is :
t t
2 ˙ 1
Z Z
δφ · δφ
Yφ (t ) = t δφ · δφ
s ds and Yφ = t Yφ (s ) ds
0 0
= measure of the divergence rate between two close orbits.
Periodic orbit : Yφ → 0
Quasi-periodic orbit : Yφ → 2
Chaotic orbit : Yφ is increasing with time
21. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Chaos Maps
We set :
the mass and the rotation rate of the asteroid (ellipsoid)
the initial conditions of the satellite (a=148.8km, i = 3 rad)
a the largest semi-axis of the ellipsoid
Variations of the primary shape (through the semi-axes b and c ).
Integrator : Runge-Kutta-Fehlberg with variable step
Precision : 10−12
Results of the chaos indicator MEGNO are given in the plane (b/a,c/a)
25. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
However let us remind that the mass is constant in these graphics, some of
these cases correspond to impossible values of the densities (chosen between 1
and 3 gr/cm3 ) - The mass M and the axis a are xed.
26. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Evolution of the MEGNO with time
After 0.1 year after 1 year
after 5 years after 10 years
27. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Spin
v = −2.5 10−4 rad/s v = −4.0 10−4 rad/s
v = −3.76687 10−4 rad/s Inuence of the spin v
28. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Semi major-axis
a =130 km a =170 km
a =148.8 km Evolution with semi-major axis
29. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Reference case
M=3.895551 106 kg, initial orbit i 3 rad)
rotation rate v = −3.76687 × 10−4 rad/s
30. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Gravitational resonance
A resonance between
the rotation of the primary (P = 4, 63 hours)
the orbital period of the satellite (specic to each point)
Tests on a few points
Q1 : b=18.6 km, c=8.9 km and Y → 2 - period of 2.50 days
Q2 : b=18.9 km, c=8.9 km and Y → +∞ - period of 2.48 days
Q3 : b=20.1 km, c=8.9 km and Y → 2 - period of 2.48 days
Gravitational resonance 1:13
31. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Frequency analysis (J. Laskar)
c= 8.9 km is constant and b varies
Analysis (a ∗ cos (M ), a ∗ sin(M )) :
32. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Second case
M=3.745722 106 kg, i 2.99), v = −3.76687 × 10−4 rad/s
33. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Choosing again c = 8.9 km and b varies with time
Analysis of (a ∗ cos (M ) , a ∗ sin(M ))
34. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Analytical development
MacMillan Potential for an ellipsoid (1958) :
V (x , y , z ) = 3 GM
+∞
x2 y2 z2 ds
Z „ «
1− − − √ √
2 λ1 s2 s 2 − h2 s2 − k2 s 2 − h2 s 2 − k 2
with h2 = a2 − b2 and k 2 = a2 − c 2
a, b et c are the semi- axes of the ellipsoid with a ≥ b ≥ c .
Chauvineau, B., Farinella, P. and Mignard, F. (Icarus, 1993)
Planar orbits about a triaxial body - Application to asteroidal
satellites
Scheeres, D. (Icarus, 1994) Dynamics about uniformly rotating
triaxial ellipsoids : applications to asteroids
35. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Expansion of the potential
Expansion of MacMillan potential in powers of h/R and k /R
where R 2 = x 2 + y 2 + z 2
Keplerian orbit about a rotating body (about its vertical axis)
perturbed by MacMillan potential
√
Delaunay's Hamiltonian momentum : L = µ¯ a
µ µ 2 2 3µ 2 2 2 2
H = −
2L2 − 10R 3 (h + k ) + 10R 5 (y h + z k )
36. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
1:1 resonance, circular and equatorial
The curve corresponds to an curve : k
2 − 2h 2 0
37. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
1:1 resonance model
= L sin(M +
2
Simplications : z = 0 and y
µ − φ)
φ=v t
Resonant variable : σ = M + − φ
Same equilibria as Scheeres or others
µ µ4 2 2 3µ4 2 (1 − cos 2σ).
H =− −v L − 6 (h + k ) + h
2L2 10L 20L6
The exact 1:1 resonance : v =n: k
2 − 2h2 = 0
38. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Other resonances in the equatorial cases
= L sin(f +
2
z = 0 and y
µ − φ)
The eccentricity is used to develop f in multiples of M
Extraction of the resonant angle σ
σ is now conjugated to P = L − G .
Introduction of the pericentre motion (second degree of
freedom) responsible for the multipliers of the exact resonance
Higher orders of resonances require higher powers of the
eccentricity
Case Ida - Dactyl : potential 5:1 or 9:2 resonance (eccentricity
of Dactyl high)
39. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Non-equatorial cases : polar case
Map of the resonances between the rotation of Vesta and the
orbital motion of a polar satellite : numerical work
LAMO HAMO
14
1000 13
Paper of Tricarico and Sykes
The dynamical environment of Vesta
12
900 11
800
10 submitted to Planetary and Space Science
1:2 9
Distance Range [km]
Orbital Period [hour]
8
700
7
2:3
600 6
5
500
1:1 4
400
3
4:3
3:2
300 2
300 400 500 600 700 800 900 1000
Initial Radius [km]
Figure 4: Distance range as a function of the initial radius of a circular orbit, computed over a
period of 50 days. The central mark in each bar represents the median of the range. The rotation
period used for Vesta is of 5.3421288 hours (Harris et al., 2008). Five spin-orbit resonances have
been identified and marked in the plot. The 1:1 resonance affects the largest interval in initial
radius, but the strongest perturbations come from the 2:3 resonance. The leftmost data point,
40. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Our results
Numerical integration with NIMASTEP (especially drawn for
polar orbits)
Resonance map : position and importance of each resonance
Complete agreement with Tricarico and Sykes
Discovery of smaller structures ignored by Tricarico and Sykes
Analysis of each resonance to compare their width and shape
41. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
42. Introduction Satellites of asteroids Stability tests Chaos Maps Analytical development Conclusions
Conclusions
MEGNO is very ecient for the detection of gravitational
resonances
Use of the frequency map for the identication of the
resonances
Eciency and precision of MacMillan potential for ellipsoidal
bodies
Explicit approximated formulation in h and k
Specic i : j resonance models : strength, width, equilibria
Equatorial and polar cases (Ida and Vesta)
Paolo's contribution : pioneer and omnipresent in the
literature about asteroid dynamics