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Chandra X-ray Observatory is third of four great observatories.

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Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. Chandra X-ray Observatory was named in honor of Indian-American physicist Subrahmanyan Chandrasekhar who is known for determining the mass limit for White Dwarf stars to become Neutron stars. "Chandra" also means "moon" or "luminous" in Sanskrit.

Chandra X-ray Observatory.
Artist's Illustration of the Chandra X-ray Observatory in orbit (credit: NASA / MSFC).
Organization NASA, SAO, CXC
Wavelength regime X-ray
Orbit height 10,000 km (perigee), 140,161 km (apogee)
Orbit period 64 h and 18 min
Launch date 23 July 1999
Deorbit date ?
Mass 4800 kg
Other names Advanced X-ray Astrophysics Facility, AXAF
Webpage chandra.harvard.edu/
Physical Characteristics
Telescope Style 4 nested pairs of grazing incidence paraboloid and hyperboloid mirrors
Diameter 1.2 m
Collecting Area 400 cm² at 1 keV
Focal Length 10 m
ACIS imaging spectrometer
HRC camera
HETGS high resolution spectrometer
LETGS high resolution spectrometer

There will be four Great Observatories. The first was Hubble Space Telescope; second the Compton Gamma Ray Observatory, launched in 1991; and last is the Spitzer Space Telescope. Prior to successful launch, the Chandra Observatory was known as AXAF, the Advanced X-ray Astrophysics Facility. AXAF was assembled and tested by TRW in Redondo Beach, California.

Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes, requiring a space-based telescope to make these observations.

Discoveries by Chandra X-ray Observatory.

  • "observations of the bullet cluster (puts) limits on the cross-section of the self-interaction of dark matter.".
  • The first light image, of supernova remnant Cassiopeia A, gave Astronomers their first glimpse of the compact object at the center of the remnant, probably a neutron star or black hole. (Pavlov, et al, 2000).
  • In the Crab Nebula, another supernova remnant, Chandra showed a never-before-seen ring around the central pulsar and jets that had only been partially seen by earlier telescopes. (Weisskopf, et al., 2000).
  • The first X-ray emission was seen from the supermassive black hole, Sagittarius A - , at the center of the Milky Way. (Baganoff, et al, 2001).
  • Chandra X-ray Observatory found much more cooler gas than expected spiralling into the center of the Andromeda Galaxy.
  • Pressure fronts were observed in detail for the first time in Abell 2142, where clusters of Galaxies are merging.
  • The earliest images in X-rays of the shock wave of a supernova were taken of
  • Chandra showed for the first time the shadow of a small Galaxy as it is being cannibalized by a larger one, in an image of Perseus A.
  • A new type of black hole was discovered in Galaxy M82, mid-mass objects purported to be the missing link between stellar-sized black holes and supermassive black holes. (Griffiths, et al., 2000).
  • X-ray emission lines were associated for the first time with a gamma-ray burst, GRB 991216. (Piro, et al., 2000).
  • High school students, using Chandra X-ray Observatory data, discovered a neutron star in supernova remnant IC 443.
  • Observations by Chandra X-ray Observatory and BeppoSAX suggest that gamma-ray bursts occur in star-forming regions.
  • Chandra data suggested that RX J1856.5-3754 and 3C58, previously thought to be pulsars, might be even denser objects: quark stars. These results are still debated.
  • TWA 5B, a brown dwarf, was seen orbiting a binary system of Sun-like stars.
  • Nearly all stars on the main sequence are X-ray emitters. (Schmitt & Liefke, 2004).
  • Sound waves from violent activity around a supermassive black hole were observed in the Perseus Cluster.
  • The X-ray shadow of Titan was seen when it transitted the Crab Nebula.
  • X-ray emissions from materials falling from a protoplanetary disc into a star. (Kastner, et al., 2004).
  • Hubble constant measured to be 76.9 km/s/Mpc using Sunyaev-Zel'dovich effect.
  • 2006 Chandra X-ray Observatory found strong evidence that Dark matter exists by observing supercluster collision.
  • 2006 X-ray emitting loops, rings and filaments disovered around a supermassive black hole within Messier 87 imply the presence of pressure waves,shock waves and sound waves. The evolution of Messier 87 may have been dramatically affected.

Technical description of Chandra X-ray Observatory.

Unlike optical Telescopes which possess simple silvered parabolic surfaces (mirrors), X-ray Telescopes generally have nested cylindrical paraboloid and hyperboloid surfaces coated with iridium. X-ray photons would be absorbed by normal mirror surfaces, so mirrors with a low grazing angle are necessary to reflect them. Chandra X-ray Observatory uses four pairs of nested mirrors, together with their support structure, called the High Resolution Mirror Assembly (HRMA).

Chandra's high elliptical orbit allows it to observe continuously for up to 55 hours of its 65 hour orbital period.

With an angular resolution of 0.5 arcsecond (2.4 µrad), Chandra X-ray Observatory possesses a resolution over one thousand times better than that of the first orbiting X-ray telescope, which had less precise gold-coated mirrors.

Instruments on board Chandra X-ray Observatory.

The Science Instrument Module (SIM) holds the two focal plane instruments, the Advanced CCD Imaging Spectrometer (ACIS) and the High Resolution Camera (HRC), moving whichever is called for into position during an observation.

ACIS consists of 10 CCD chips and provides images as well as spectral information of the object observed. It operates in the range of 0.2 - 10 keV. HRC has two micro-channel plate components and images over the range of 0.1 - 10 keV. It also has a time resolution of 16 microseconds. Both of these instruments can be used on their own or in conjunction with one of the observatory's two transmission gratings.

The transmission gratings, which swing into the optical path behind the mirrors, provide Chandra with high resolution spectroscopy. The High energy Transmission Grating Spectrometer (HETGS) works over 0.4 - 10 keV and has a spectral resolution of 60-1000. The Low energy Transmission Grating Spectrometer (LETGS) has a range of 0.09 - 3 keV and a resolution of 40-2000.

History of Chandra X-ray Observatory.

Chandra X-ray Observatory.
Chandra X-ray Observatory sits inside the payload bay on Space Shuttle Columbia mission STS-93.

In 1976 the Chandra X-ray Observatory (called AXAF at the time) was proposed to NASA by Riccardo Giacconi and Harvey Tananbaum. Preliminary work began the following year at Marshall Space Flight Center (MSFC) and the Smithsonian Astrophysical Observatory (SAO). In the meantime, in 1978, NASA launched the first imaging X-ray telecope, Einstein (HEAO-2), into orbit. Work continued on the Chandra X-ray Observatory project through the 1980's and 1990's. In 1992, to reduce costs, the Spacecraft was redesigned. Four of the twelve planned mirrors were eliminated, as were two of the six scientific instruments. Chandra X-ray Observatory's planned orbit was changed to an elliptical one, reaching one third of the way to the Moon's at its farthest point. This eliminated the possibility of improvement or repair by the Space Shuttle but put the observatory above the Earth's radiation belts for most of its orbit.

AXAF was renamed Chandra X-ray Observatory in 1998 and launched in 1999 by the shuttle Columbia (STS-93). Chandra X-ray Observatory was the heaviest payload ever launched by the shuttle, a consequence of the Inertial Upper Stage booster rocket system needed to transport the Spacecraft to its high orbit.

Chandra has been returning data since the month after it launched. It is operated by the SAO at the Chandra X-ray Center in Cambridge, Massachusetts, with assistance from MIT and Northrop Grumman Space Technology. The ACIS CCDs suffered particle damage during early radiation belt passages. To prevent further damage, the instrument is now removed from the telescope's focal plane during passages.

In 2004Chandra X-ray Observatory celebrated its fifth year of operation.

More About Chandra X-Ray Observatory.

Chandra Looks at the Earth's Aurora

Dec 29, 2005 - A team of scientists turned the Chandra X-Ray Observatory back at the Earth, and closely observed the north polar region ten times during 2004. They have discovered low-energy (0.1 - 10 kilo electron volts) X-ray emissions from the Earth's auroral activity. The colour of the X-ray arcs represent the intensity of the X-ray generation, with red indicating the maximum brightness.

1000 Year-Old Supernova Remnant

Dec 16, 2005 - NASA's Chandra X-Ray Observatory has taken a new photograph of SN 1006; a supernova that appeared in the sky in 1006, and blazed more brightly than Venus. We now know that SN 1006 announced the death of a star located approximately 7,000 light years from Earth. It's likely that a white dwarf star was siphoning matter away from a companion star. When its mass exceeded the limit of stability, it exploded.

A Supernova in Progress

Nov 29, 2005 - This image taken by the Chandra X-Ray Observatory shows the ongoing expansion of supernova SN 1970G, which exploded more than 35 years ago. Astronomers estimate that the shockwaves from the supernova will crash into shells of material shed by the star about 25,000 years ago, completing its transition into a supernova remnant.

Side-by-Side Supernova Remnants

Nov 15, 2005 - This unique photograph, taken by NASA's Chandra X-Ray Observatory, contains not one, but two supernova remnants. The pair are known as DEM L316, and they're located in the Large Magellanic Cloud galaxy. The gas shell at the upper-left contains considerably much more iron, so it's probably the product of a Type 1a, triggered by the infall of matter from a companion star onto a white dwarf. The lower-right shell is a Type II supernova, the remains of a massive star that exploded a few million years into its short life.

Chandra View of Tycho's Remnant

Sep 22, 2005 - In 1572, Danish astronomer Tycho Brahe observed and studied an exploding star that would later be named after him. NASA's Chandra X-Ray Observatory shows that the Tycho's Supernova remnant is an expanding bubble of debris which is inside a larger bubble of high-energy electrons. Astronomers think that remnants like this could be a source of cosmic rays; high-energy nuclei found throughout the galaxy which constantly bombard the Earth.

Bright Young Stars in Trumpler 14

Sep 1, 2005 - This newest image released by the Chandra X-Ray Observatory shows the star cluster Trumpler 14. This cluster is located about 9,000 light years away from Earth and contains about 1,600 stars. It has one of the highest concentrations of massive, luminous stars in the Milky Way. The bright stars in the cluster are very young - less than 1 million years old - and will explode within a few million more years as powerful supernovae.

Supernova Shockwave Slams into Stellar Bubble

Aug 18, 2005 - One of the most famous supernovae in recent memory is SN 1987A, which exploded in the Large Magellanic Cloud. Before its death, the star produced a ferocious stellar wind that carved out a large bubble in the surrounding, colder gas. When it went supernova, a shockwave traveled out in space, and astronomers have been waiting in anticipation for the shockwave to slam into the edge of this bubble. New images from NASA's Chandra X-Ray Observatory shows that this stage now appears to be underway.

How Millisecond Pulsars Spin So Fast

Jul 20, 2005 - Observations with the Chandra X-Ray Observatory have given astronomers some clues about what causes millisecond pulsars - extremely dense stars which can spin many times a second. Several of these pulsars were discovered in a stellar cluster called 47 Tucanae, where the stars are less than.1 light years apart. Astronomers think these pulsars started as regular neutron stars, but tightly joined with stellar companions they picked up in the cluster. Eventually they get so close they start drawing material off the companion, which causes them to speed up.

White Dwarfs in a Death Spiral

May 31, 2005 - New observations from the Chandra X-Ray Observatory have discovered two white dwarf stars orbiting one another at a tremendous speed - they're only 80.000 km (50,000 miles) apart! The rate at which they're orbiting is decreasing by 1.2 milliseconds every year, which means they're destined to eventually collide. What's important about this find is that the stars are probably creating gravity waves, as predicted by Einstein, and these gravity waves should increase as they get closer and closer.

Chandra Sees a Bridge Between Stars

Apr 28, 2005 - Astronomers have theorized that Mira AB is a binary star system consisting of an evolved red giant star and a white dwarf star, and now the Chandra X-Ray Observatory has been able to resolve their relationship. Chandra can actually resolve the stream of matter flowing off the red giant, which is then captured by the white dwarf. This matter heats up as it bunches up around the white dwarf, and blazes in the X-ray spectrum. Mira AB is only 450 light-years away, and the stars are separated by approximately twice the distance of the Sun and Pluto.

Ghostly Supernova Remnant

Apr 19, 2005 - The Chandra X-Ray Observatory spent 150 hours examining supernova remnant G21.5-0.9, revealing a beautiful ghostly shell. The shell is created by the shockwave of particles ejected by the supernova explosion as they slam into material that was sloughed off earlier by the star. This shockwave heats the surrounding material to millions of degrees causing it to blaze in the X-ray spectrum visible to Chandra. The star that produced this explosion was probably 10 times larger than the Sun.

Missing Matter Could Be Clouds of Gas

Feb 2, 2005 - NASA's Chandra X-Ray Observatory has located two huge clouds of interstellar hot gas that could partially explain where all the matter is in the Universe (we're not talking about Dark Matter here, just regular matter that hasn't been seen yet). Computer simulations predicted that this missing matter could form into a weblike structure of gas clouds, from within which clusters of galaxies formed. These clouds have defied detection until now because of their low density. Astronomers used Chandra to watch a distant galaxy which has been brightening for about 2 years. Their data showed that two separate clouds of gas containing ions of carbon, nitrogen, oxygen, and neon were absorbing X-rays from this galaxy.

Biggest Eruption in the Universe

Jan 6, 2005 - Astronomers have used the Chandra X-Ray Observatory to watch the most powerful eruption ever seen in the Universe. The eruption is coming from the heart of a distant galaxy cluster called MS 0735.6+7421; it's been going on for more than 100 million years, and generated the equivalent energy of hundreds of millions of gamma-ray bursts. Astronomers believe that this energy is being released because a supermassive black hole has sucked in more matter than it can consume - the mass of 300 million Suns is being swallowed - and this excess is generating tremendous heat as it backs up.

Giant Star Generates a Massive Amount of X-Rays

Jan 4, 2005 - The Chandra X-Ray observatory took this image of an unusual star called Beta Ceti. It's only three times more massive than our own Sun, but it radiates 2,000 times more X-ray power. Astronomers believe it's putting out so much X-ray radiation because it's at an advanced stage of stellar evolution called "core helium burning". For its first billion years, Beta Ceti was converting hydrogen to helium through fusion, but it ran out of hydrogen fuel and became a red giant star. Then it started to shrink again, and temperatures rose to 100 million degrees; hot enough that it could begin fusing helium atoms together to create carbon atoms.

Pulsar is Even Denser Than Prevously Thought

Dec 14, 2004 - The Chandra X-Ray Observatory took a good long look at a pulsar and found that it's cooling rapidly, and suggests that it has matter packed much more densely than scientists were expecting. An international team of astronomers used Chandra to measure the pulsar at the centre of nebula 3C58, which is the remnant from a supernova that exploded in 1181. In less than 800 years, it has cooled to less than 1 million degrees Celsius - for pulsars, that's cold. The cooling depends on the density of the matter in the pulsar.

X-Ray Portrait of Proxima Centauri

Nov 10, 2004 - NASA's Chandra X-Ray Observatory took this image of red dwarf star Proxima Centauri, our closest stellar neighbour (after the Sun, of course). The image shows that its surface is in a constant state of turmoil, with flares occurring almost continuously. Proxima Centauri has only 1/10th the mass of our own Sun, and the conversion of hydrogen to helium happens much more slowly. This creates turbulent, convective motion throughout its interior, which stores up magnetic energy - the energy is what creates all the flares.

Dark Matter Halo Puzzles Astronomers

Oct 26, 2004 - Astronomers using the Chandra X-Ray Observatory have discovered a huge halo of dark matter around an isolated elliptical galaxy; an object that shouldn't have such a halo, according to optical observations. The galaxy, NGC 4555, is unusual that it's a large elliptical galaxy which isn't part of a larger cluster of galaxies. It's surrounded by a cloud of gas, twice the size of the galaxy itself, that's been heated to 10-million-degrees Celsius. This gas could only get that hot if it was being constrained by a halo of dark matter ten times the mass of the stars in the galaxy.

It's Not a Comet, It's a Pulsar

Sep 23, 2004 - The Chandra X-Ray Observatory took this image of a pulsar surrounded by high-energy particles as it plows through interstellar space. The pulsar is hurtling to the left in this image at a speed of 2.1 million kph (1.3 million mph), and the particles are being blasted back like the tail on a comet. The pulsar is known as "The Mouse", aka G359.23-0.82, and it was discovered in 1987 by radio astronomers using the Very Large Array in New Mexico. Because it's moving so quickly and interacting so visibly with its environment, astronomers have a unique opportunity to understand pulsar magnetic fields, and how they eject material.

Double Jets Around Exploded Star

Aug 23, 2004 - This is a detailed image of an exploded star called Cassiopeia A, taken by the Chandra X-Ray Observatory. The space-based observatory focused on this remnant for 1 million seconds (just over 11 days), and revealed the bright outer green ring 10 light years across which was generated by the shockwave from the supernova explosion. Two large jets extend outside this shockwave on opposite sides, and contain large quantities of silicon. This means they were formed early on in the explosion; otherwise, they'd contain mostly iron from the star's central regions.

Chandra Sees Clouds Coming Together

Aug 16, 2004 - A new image of Abell 2125, taken by the Chandra X-Ray Observatory, shows several intergalactic clouds of hot gas in the process of merging together; they seem to be in the process of creating a single massive galaxy cluster. Chandra's resolution allows astronomers to distinguish the clouds from the individual galaxies inside it.

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