Astronomical instruments can be divided into two categories: observational instruments used to observe celestial objects directly, and auxiliary instruments used to analyze and record observational data. Observational instruments include telescopes, which enable objects invisible to the naked eye to be seen or detected. The two main types of telescopes are optical telescopes, which use lenses or mirrors to collect and magnify light, and radio telescopes, which detect radio waves emitted by celestial objects. Radio telescopes often use interferometry with arrays of antennas to achieve high resolution. Large optical and radio telescopes around the world are listed with their key characteristics.
Use principles of reflection and refraction to describe how lenses and mirrors work.
**More good stuff available at:
www.wsautter.com
and
http://www.youtube.com/results?search_query=wnsautter&aq=f
Describe how layers of rocks (stratified rocks) are formed,
Describe the different methods (relative and absolute dating) to determine the age of stratified rocks, and
Explain how relative and absolute dating were used to determine the subdivisions of geologic time.
The relative age of a rock is its age when compared with the ages of other rocksThe absolute age of a rock is a calculation of the number of years that have passed since the rock formed.
Use principles of reflection and refraction to describe how lenses and mirrors work.
**More good stuff available at:
www.wsautter.com
and
http://www.youtube.com/results?search_query=wnsautter&aq=f
Describe how layers of rocks (stratified rocks) are formed,
Describe the different methods (relative and absolute dating) to determine the age of stratified rocks, and
Explain how relative and absolute dating were used to determine the subdivisions of geologic time.
The relative age of a rock is its age when compared with the ages of other rocksThe absolute age of a rock is a calculation of the number of years that have passed since the rock formed.
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.
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
We report the discovery of an optical Einstein Ring in the Sculptor constellation,
IAC J010127-334319, in the vicinity of the Sculptor Dwarf Spheroidal Galaxy. It is
an almost complete ring ( 300◦) with a diameter of 4.5 arcsec. The discovery was
made serendipitously from inspecting Dark Energy Camera (DECam) archive imaging
data. Confirmation of the object nature has been obtained by deriving spectroscopic
redshifts for both components, lens and source, from observations at the 10.4 m Gran
Telescopio CANARIAS (GTC) with the spectrograph OSIRIS. The lens, a massive
early-type galaxy, has a redshift of z = 0.581 while the source is a starburst galaxy
with redshift of z = 1.165. The total enclosed mass that produces the lensing effect
has been estimated to be Mtot = (1.86 ± 0.23) · 1012M⊙.
Hubble Telescope is used to observe in the near-infrared through the visible spectrum to the ultra-violet.
This Telescope is placed above the distortion of the atmosphere, far above rain clouds and light pollution.
Its advantage to avoid atmospheric turbulence.It has an extremely large field of view which is necessary to obtain high resolution images of large areas of the sky.
The extremely high albedo of LTT 9779 b revealed by CHEOPSSérgio Sacani
Optical secondary eclipse measurements of small planets can provide a wealth of information about the reflective properties
of these worlds, but the measurements are particularly challenging to attain because of their relatively shallow depth. If such signals
can be detected and modeled, however, they can provide planetary albedos, thermal characteristics, and information on absorbers in
the upper atmosphere.
Aims. We aim to detect and characterize the optical secondary eclipse of the planet LTT 9779 b using the CHaracterising ExOPlanet
Satellite (CHEOPS) to measure the planetary albedo and search for the signature of atmospheric condensates.
Methods. We observed ten secondary eclipses of the planet with CHEOPS. We carefully analyzed and detrended the light curves using
three independent methods to perform the final astrophysical detrending and eclipse model fitting of the individual and combined light
curves.
Results. Each of our analysis methods yielded statistically similar results, providing a robust detection of the eclipse of LTT 9779 b
with a depth of 115±24 ppm. This surprisingly large depth provides a geometric albedo for the planet of 0.80+0.10
−0.17, consistent with
estimates of radiative-convective models. This value is similar to that of Venus in our own Solar System. When combining the eclipse
from CHEOPS with the measurements from TESS and Spitzer, our global climate models indicate that LTT 9779 b likely has a super
metal-rich atmosphere, with a lower limit of 400× solar being found, and the presence of silicate clouds. The observations also reveal
hints of optical eclipse depth variability, but these have yet to be confirmed.
Conclusions. The results found here in the optical when combined with those in the near-infrared provide the first steps toward
understanding the atmospheric structure and physical processes of ultrahot Neptune worlds that inhabit the Neptune desert.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
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Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
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We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Let's dive deeper into the world of ODC! Ricardo Alves (OutSystems) will join us to tell all about the new Data Fabric. After that, Sezen de Bruijn (OutSystems) will get into the details on how to best design a sturdy architecture within ODC.
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The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
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2. Astronomical instruments can be divided into two
major categories. The first category might include
all of the instruments which are used in the actual
process of observing celestial objects. Some of
these, like the meridian transit, are designed for
specific tasks such as the precise determination of
an observer's position on the earth or a star's
position in the sky; other observational
instruments are principally collectors of the
radiation emitted by stars, planets, nebulas, and
galaxies. These latter, which are generally referred
to as telescopes, enable objects invisible to the
naked eye to be seen, photographed, or otherwise
detected.
3. In the second category may be grouped the auxiliary
instruments which are used to standardize, record, or
analyze the data obtained by the observational
equipment. Devices to provide an accurate standard of
time, to determine the brightnesses of stars, to record
their spectra, or to measure the positions of stars on
photographic plates, are examples of instruments
belonging to this second category.
4. It should be mentioned at the outset that the radiation
gathered from a celestial object by a conventional
astronomical telescope lies in the visible and near visible
region of the electromagnetic spectrum. Over the past few
decades, however, an entirely different type of astronomical
telescope has come into wide use. These instruments, known
as radio telescopes, have been developed as the result of the
discovery in 1928-1932 by Karl G. Jansky of the Bell Telephone
Laboratories that the center of our own galaxy is a powerful
emitter of electromagnetic radiation in the radio wavelength
region. Since Jansky's initial discovery, many other celestial
"radio sources" have been found. The operating
principles and the evolution of radio telescopes, as well as the
significance and importance of the new field of radio
astronomy which they have fostered, are treated under Radio
Astronomy and Radar Astronomy. Also described elsewhere
are certain other electronic devices, such as "image
intensifiers," which already belong, or soon will belong, to the
growing list of techniques employed in modern astronomy.
5. Optical Telescopes
Optical Telescopes -- The purpose of a telescope is to collect light
and then to have the image magnified. The larger the telescope's
main light-collecting element, whether lens or mirror, the more
light is collected. It is the total amount of light collected that
ultimately determines the level of detail. All optical telescopes fall
into one of three classes (see Figure 01). In the refracting
telescope, light is collected by a 2-element objective lens and
brought to a focal plane. By contrast the reflecting telescope uses
a concave mirror for this purpose. The mirror-lens, or
catadioptric, telescope employes a combination of both mirrors
and lenses, resulting in a shorter, more portable optical tube
assembly. All telescopes use an eyepiece (located behind the focal
plane) to magnify the image formed by the primary optical
system. Other instruments can be placed in the focal plane for
various purposes, e.g., a photo-electric cell to measure the
luminosity, the slit of a spectrograph to analyse the light, or a
thermo-couple to measure temperature. The advantage of
reflecting telescope is that it has no chromatic aberration.
Moreover, mirrors can be manufactured to much larger
dimensions
6. than lenses. Large lenses sage in the middle and distort the received
image. Reflectors can also be made from a great variety of materials,
because all that matters is the reflecting surface, whereas lenses have to
be made from special types of glass. Figure 02a is the aerial view of
Mauna Kea in Hawaii. It shows the domes that house many of the world's
largest telescopes.
7. Figure 01 Telescope, Types
Figure 02a Mauna Kea
The magnification of a telescope is given by the formula:
M = OF / f, -------------------- (1)
where OF is the focal length of the objective, and f that of
the eyepiece.
The resolution (limit) of a telescope is given by the
formula:
R (in sec of arc) = 2.3 x 105 x ( /A), ------------------- (2)
where is the wavelength and A is the diameter of the
aperture. For example, if A = 100 cm and = 4000x10-8
(yellow light) then R = 0.092".
8. Interferometer is used to measure the size of
astronomical objects. By careful analysis of
the resulting interference pattern, the
position of a point source, or fine detail in
an extended one, can be resolved. The same
formula for the resolution above is
applicable except the aperture A is replaced
by the baseline between the two receivers.
This technique has been used extensively
with radio telescopes; it is now also applied
to the optical telescopes as well.
The table below lists some of the optical
telescopes in the world (a complete listing
can be found in reference 1):
9. Observatory Location Aperture (m) Characteristics
Keck Mauna Kea, Hawaii 10.0 36 segment mirror
Keck II Mauna Kea, Hawaii 10.0 Interferometry optical
Hobby-Eberly Mt. Fowlkes, Texas 9.2 inexpensive, spectroscopy only
Observational performance
Subaru Mauna Kea, Hawaii 8.3
optimized
4 units combined as an
VLT (Very Large Telescope) Cerro Paranal, Chile 8.2
interferometer
Gemini North Mauna Kea, Hawaii 8.1 Twin of Gemini South
All sky coverage with Gemini
Gemini South Cerro Pachon, Chile 8.1
North
Next Generation Space Telescope Halo orbit 7-9 Scheduled for launch in 2007
Previous generation (1950-1990)
Hale Mt. Palomar, Ca., 5.0
limit
New Technology Cerro La Silla, Chile 3.5 Adaptive opticsa
Discovery of cosmic expansion
Hooker Mt. Wilson, Ca 2.5
(1917)
Observations outside the
Hubble Space Telescope Low Earth orbit 2.4
atmosphere
Solar Tower Kitt Peak, Arizona 1.8 Study of the Sun
Yerkes Williams Bay, Wisconsin, 1.0 World's largest refractor (1897)
10. Table 01 Optical Telescopes
Figure 02b Large Telescopes of the World
By 2010 there are about 50 telescopes on Earth with at
least 2.5 meters in aperture diameter. Figure 02b below
shows the locations for these giant telescopes (from
"Astronomy", Vol. 38, Issue 11, November 2010).
11. Radio Telescopes · Radio Telescopes -- It is an instrument for
collecting radio waves from celestial objects.
The radiation is reflected from a parabolic
dish to an aerial (dipole), situated at the
focus, from which the signals are led to a
radio receiver. Because the wavelength of
radio waves is very large (from 0.3 mm to 30
cm), a radio telescope with an aperture
comparable to the optical telescope would
have a very poor resolution according to Eq.
(2). A considerable increase in resolution
can be obtained by using an interferometer
- an array of identical antennae spaced at
regular intervals as shown in Figure 03,
which shows that the elevation angle of a
celestial object (from the horizon) can be
calculated from the time difference and the
distance between the receivers (the
baseline). The angular separation
(resolution) is obtained from the difference
of the elevation angles corresponding to the
resolution of the time difference of T1 and
T2.
12. Interferometer
The table below lists some of the radio telescopes in the world:
Observatory Location Resolution (arcsec) Characteristics
Very Long Baseline
VLBI Intercontinental > 0.001
Interferometer
Largest (dish) synthesis
VLA Socorro, NM > 0.04
array
Arecibo Puerto Rico > 0.2 Largest fixed dish
Effelsberg Effelsberg, Germany > 0.6 Largest single dish
Largest in southern
Parkes NSW, > 0.9
hemisphere
Table 02 Radio Telescopes
13. Infrared Telescopes
Infrared Telescopes -- Infrared radiation
(wavelength between 1 and 1000 mm) from space
is mostly absorbed by the atmosphere (see Figure
04): so the largest infrared telescopes are built on
the tops of high mountains, installed on special
high flying aircraft or balloons, or better yet on
satellites orbiting the earth. However, atmospheric
absorption is not the only obstacle to analyse this
type of radiation on earth: the main problem,
which also occurs in space, is to distinguish the
signal collected from the "background noise", i.e.,
from the enormous infrared emissions of the Earth
or
14.
15. of the instruments themselves, since object
which is not at absolute zero, emits infrared
radiation. So everything around the
instruments (including the telescope)
produces "backround noise". Therefore,
special photo- graphic film is used to
produce a "thermograph" of a
celestial body, and the instruments must be
cooled continuously by immersion in liquid
nitrogen or helium (Figure 05).
16. Figure 04 Atomspheric Absorption
Figure 05 Infrared Telescope
The table below lists some of the infrared telescopes in the world:
Observatory Location Aperture (m) Date
UKIRT Mauna Kea, Hawaii 3.8 Since 1978
To be launched in
FIRST Orbiting 3.0
2007
NASA IRTF Mauna Kea, Hawaii 3.0 Since 1979
Started operation in
SOFIA Airborne 2.5
February, 2006
Launched in August,
SIRTF Heliocentric orbit 0.85
2003
Launched in
ISO Geocentric orbit 0.6
November, 1995
Operated for ten
IRAS Geocentric orbit 0.6
months in 1983
Table 03 Infrared Telescopes
17. Acronym: UKIRT - United Kingdom Infrared
Telescope.
FIRST - Far Infrared Space Telescope.
IRTF - Infrared Telescope Facility.
SOFIA - Stratosphere Observatory for
Infrared Astronomy.
SIRTF - Space Infrared Telescope Facility;
renamed to Spitzer Space Telescope in honor of the
late
astrophysicist Lyman Spitzer Jr.,
who first conceived of a large telescope in orbit.
ISO - Infrared Space Observatory.
IRAS - Infrared Astronomical Satellite.
18. High Frequency Observations
Observations of High
Frequency Radiation --
As shown in Figure 04,
radiation with
wavelength shorter than
310 nm are absorbed in
the Earth's
stratosphere, high
above any terrestrial
observatory. These
short wavelength
radiations can be
studied only by
instruments carried on
very-high--altitude
balloons, rockets,
satellites, and
19. Figure 06 Grazing Telescope
Figure 07 Scintillator
Although attempts to study the sun's UV spectrum
from balloons were made during the 1920s, it was not
until 1946 that rocket-borne instruments made this
possible. Only limited additional progress was made
until 1962, when the first Orbiting Solar Observatory
(OSO) satellite was launched by the National
Aeronautics and Space Administration (NASA). It
returned thousands of UV spectra, including the first
exteme-ultraviolet (wavelengths below 91 nm)
observations of the solar corona. The International
Ultraviolet Explorer (IUE) was in orbit between 1978
and 1996.
20. Its large telescope (0.45 m aperture) made possible
the first UV observations of objects beyond the
Milky Way. The Extreme Ultraviolet Explorer
(EUVE, 1990-1999) was the first orbiting
observatory to focus on that part of the spectrum.
Ultraviolet spectroscopy has been particularly
valuable because many of the most abundant
atoms and ions in the universe have their strongest
lines in that region of the spectrum. Right now
there are no dedicated ultraviolet observatories in
orbit. The Hubble Space Telescope can perform a
great deal of observing at ultraviolet wavelengths,
but it has a very fairly small field of view.
21. X-rays are typically emitted by gaseous bodies with
temperatures ranging from 106 to 108 oK. Conventional
telescopes cannot be used at x-ray (or EUV) wavelengths
because mirrors abosrb x-rays rather than reflect them,
unless the x-rays graze the surface at a very shallow
angle. Satellites such as ROSAT (in orbit between 1990-
1999), and the Chandra X-ray observatory (since July,
1999) utilize "grazing incidence" telescopes (GRITs),
which bring x-rays to a focus by reflecting them at
shallow angles from the surfaces of nested sets of
tapering, tubelike reflectors as shown in Figure 06. X-
ray observations have discovered a variety of objects,
ranging from hot patches and cool "holes" in the Sun's
outer atmosphere to swirling discs of hot gas
surrounding collapsed stars and black holes to hot
clouds of gas in intergalactic space.
22. Gamma rays are the most energetic form of
electromagnetic radiation. Because their wavelengths
are far smaller than the sizes of the atoms in a mirror,
gamma rays cannot be focued by reflection, and the
early gamma-ray satellites were unable to form images
of sources or even determine their positions with
confidence. Modern gamma-ray imaging systems and
spectrometers, such as those carried on board the
Compton Gamma Ray Observatory (CGRO, 1991-2000),
make use of scintillators (see Figure 07), which are
devices that convert gamma rays into visible photons
that are more easily detected and analyzed. Among
known gamma-ray sources are the Milky Way, some
pulsars, and some
23. quasars. Most puzzling of all are the 2600 gamma-ray
bursts detected by CGRO. The next generation
gamma-ray observatory is GLAST (Gamma-ray Large
Area Space Telescope) scheduled to be launched in
2005. It is designed for making observations of
celestial gamma-ray sources in the energy band
extending from 20 MeV to more than 300 GeV. Figure
08a is a gamma-ray sky animation - constructed from
simulating the first 55 days of GLAST observations of
cosmic gamma-ray sources. It shows the plane of our
Milky Way Galaxy as a broad U-shape, with the center
of the galaxy toward the right. Besides the diffuse
Milky Way glow, the simulated objects include flaring
active galaxies, pulsars, gamma-ray bursts, the flaring
Sun, and the gamma-ray Moon. The GLAST was
24. Figure 08a Gamma-ray
Sky
finally launched on June 11, 2008 many years behind schedule. It will study
gamma-rays from extreme environments in our own Milky Way galaxy, as
well as supermassive black holes at the centers of distant active galaxies,
and the sources of powerful gamma-ray bursts.
25. Figure 08b is another GLAST
gamma-ray sky map taken in
the period from August 4 to
October 30, 2008. The map
highlights the "top ten" list
of five sources within, and
beyond the Milky Way.
Within our galaxy: the Sun
traces a faint arc across the
sky during the observation
dates, LSI +61 303 is an X-ray
binary star, PSR J1836+5925
is a type of pulsar that is only
seen to pulse at gamma-ray
energies, and 47 Tuc is a
globular star cluster.
Figure 08b Gamma-ray Sky
26. A fifth galactic source (unidentified), just
above the center of the galactic plane, is a
variable source and has no clear counterpart
at other wavelengths. Beyond our galaxy:
NGC 1275 is a large galaxy at the heart of the
Perseus galaxy cluster, while 3C 454.3, PKS
1502+106, and PKS 0727-115 are active galaxies
billions of light-years away. Another
unidentified source, seen below the galactic
plane, is likely beyond the boundaries of the
Milky Way. Its nature remains a mystery.
27. Table 04 lists the three types of gamma-ray sources in the Milky Way (MW). It is
thought that they may be associated with the unknown dark matter particle
(dmp). The mp denotes the mass of proton (nucleon).
Gamma-ray
Instrument Process Source Distribution
Energy
Annihilation of ~ 0.003 mp light Around the
INTEGRAL 511 kev
e-e+ dmp center of MW
Annihilation of ~ 60 mp Faint galactic
EGRET ~ 1 Gev
dmp neutralino background
Annihilation of ~ 20000 mp heavy Point source at
HESS ~ 100 Gev
dmp dmp MW center
28. Table 04 Gamma-ray Sources in Milky Way
Acronym: INTEGRAL - INTErnational Gamma-Ray
Astrophysics Laboratory (a space instrument
combining fine spectroscopy and imaging
of gamma-ray emissions in the energy range of 15
keV to 10 MeV ).
EGRET - Energetic Gamma Ray
Experiment Telescope (space telescope for detecting
30 MeV - 30 GeV gamma-rays).
HESS - High Energy Stereoscopic System
(a system of ground based Cherenkov Telescopes for
the investigation of cosmic gamma rays in
the 100 GeV energy range).
29. Meanwhile the Swift satellite (Figure 09) was launched
into a low-Earth orbit on November 20, 2004. Its
mission is to solve the mystery of Gamma-ray bursts
(GRBs). They are the most powerful explosions in the
Universe since the Big Bang. They occur approximately
once per day and are brief, but intense, flashes of
gamma radiation. They come from all different
directions of the sky and last from a few milliseconds
to a few hundred seconds. So far scientists do not
know what causes them. Do they signal the birth of a
black hole in a massive stellar explosion? Are they the
product of
30. Figure 09 Swift
the collision of two neutron stars? Or is it some other exotic
phenomenon that causes these bursts? Swift is designed to look for
faint bursts coming from the edge of the universe. On September
2005, astronomers announce that they have detected a cosmic
explosion (GRB) at the very edge of the visible universe. The
explosion occurred soon after the first stars and galaxies formed,
perhaps 500 million to 1 billion years after the Big Bang. It was
probably caused by the death of a massive star. It is believed that this
observation opens the door to the use of GRBs as unique and
powerful probes of the early universe.
31. The key to unravel the nature of GRB comes in part from
the discovery that they are narrowly focused beams. This
realization allowed astronomers to estimate energies for
individual bursts and hypothesize the number of total
bursts occurring over a given time interval. The usual
assumption of spherical emission would over estimate the
released energy and under estimate the number of GRB. By
2007, astronomers can link the most common type of GRB,
those lasting 20 seconds or longer, with the collapse of
massive stars about 30 or more times larger than the Sun.
While the short GRB (lasting just a few milliseconds) came
from a neutron star crashing into a black hole or another
neutron star.
32. Footnotes:
aIn adaptive optics, light from the primary mirror is
directed onto a smaller flexible mirror behind which a
large number of actuators are located. The actuators
distort the shape of the mirror to cancel out distortions
in the incoming wavefronts of light that have been
caused by the atmosphere. Wavefront distortions are
sensed by monitoring a suitable bright star, or an
artificial "star" generatged by shining a powerful laser
beam into the upper atmosphere. All these operations
are computerized. Computers have so revolutionized
astronomy, in fact, that researchers rarely look
through the telescope or work in the dome during
observations. Instead, they operate the instrument in
comfort from a control room.