Chandra X-ray Observatory is a satellite launched by NASA on July 23, 1999. It was named in honor of Indian physicist Subrahmanyan Chandrasekhar who is known for determining the mass limit for white dwarf stars to become black holes.
Chandra Observatory is the third of NASA's 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 Astronomical Facility.
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. Unlike optical telescopes which possess simple silvered parabolic surfaces (mirrors), X-ray telescopes generally have nested parabolically cylindrical surfaces coated with iridium. With an angular resolution of 0.5 arcsec, Chandra possesses a resolution over one thousand times better than the resolution of the first orbiting X-ray telescope, which had less precise gold-coated mirrors. A diffractive grating provides excellent spectral resolution compared to older X-ray missions, about 1 in 1000. Chandra can also detect variations in X-ray emissions as short as 17 microseconds. The data gathered by Chandra have opened a new field in astronomy, shedding light not only upon our own Galaxy (the Milky Way), but many other galaxies and galaxy clusters.
Some objects observed with the Chandra Observatory include:
- Cassiopeia A
- the Crab Nebula in Taurus
- M82 (a galaxy)
- M31 (Andromeda Galaxy)
- Abell 2142 (galaxy cluster)
- Wolf 359