Chandra X-ray Observatory

Chandra X-ray Observatory (CXO) is a space based satellite observatory launched by NASA in 1999. It was earlier called Advanced X-ray Astrophysics Facility (AXAF). It is in a 64 hour orbit and has been specially designed to detect X-ray emission from very hot reasons of the universe such as exploded stars, clusters of galaxies, matter around black holes etc.

Why space based observatory?

CXO is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope. This is mainly because of two reasons. Firstly, this observatory has high angular resolution of its mirrors. Secondly, since earth’s atmosphere absorbs most of the X-rays, it was placed in an orbit well beyond earth’s atmosphere.  Its data is processed at Smithsonian’s Astrophysical Observatory in Cambridge, MA.

Important discoveries by CXO

CXO has made a large number of discoveries, but some worth mentioning are a large halo of hot gas was found surrounding the Milky Way; the first light image, of supernova remnant Cassiopeia, gave astronomers their first glimpse of the compact object at the center of the remnant, probably a neutron star or black hole etc.

Key facts on Structure of CXO

Unlike optical telescopes which possess simple aluminized parabolic surfaces (mirrors), X-ray telescopes generally use a Wolter telescope consisting of nested cylindrical paraboloid and hyperboloid surfaces coated with iridium or gold. Chandra uses four pairs of nested mirrors, together with their support structure, called the High Resolution Mirror Assembly (HRMA); the mirror substrate is 2 cm-thick glass, with the reflecting surface a 33 nm iridium coating, and the diameters are 65 cm, 87 cm, 99 cm and 123 cm. The thick substrate and particularly careful polishing allowed a very precise optical surface, which is responsible for Chandra’s unmatched resolution: between 80% and 95% of the incoming X-ray energy is focused into a one-arcsecond circle. Chandra’s highly elliptical orbit allows it to observe continuously for up to 55 hours of its 65-hour orbital period. At its furthest orbital point from Earth, Chandra is one of the most distant Earth-orbiting satellites. Other navigation and orientation systems on board CXO include an aspect camera, Earth and Sun sensors, and reaction wheels. It also has two sets of thrusters, one for movement and another for offloading momentum.

It is indeed a masterpiece of NASA, the most renowned space research institute of the world. The telescope still works and will keep discovering new materials in space.

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