Exploring the Invisible Universe - Chandra X-ray Telescope

Chandra Science Center/NASA Chandra's X-ray image of Eta Carina revealed a surprise - a bright horseshoe nebula around the star

What is the powerhouse driving the explosive activity in many distant galaxies? The centers of many distant galaxies are incredible sources of energy and radiation – especially X-rays. Scientists theorize that massive black holes are at the center of these active galaxies, gobbling up any material – even a whole star – that passes too close. Detailed studies with the Chandra X-ray Observatory can probe the faintest of these active galaxies, and study not only how their energy output changes with time, but also how these objects produce their intense energy emissions in the first place.

Since X-rays are absorbed by the Earth’s atmosphere, space-based observatories are necessary to study these phenomena. To meet this scientific challenge, the Chandra X-ray Observatory, NASA’s most powerful X-ray telescope, was launched in July 1999. Complementing two other space observatories now orbiting Earth – the Hubble Space Telescope and the Compton Gamma Ray Observatory – this observatory studies X-rays rather than visible light or gamma rays. By capturing images created by these invisible rays, the observatory will allow scientists to analyze some of the greatest mysteries of the Universe.

NASA The launch of the Space Shuttle Columbia with the Chandra X-ray telescope on board

Named in honor of the late Indian-American Nobel Laureate Subrahmanyan Chandrasekhar, the observatory was formerly known as the Advance X-ray Astrophysics Facility. The Chandra X-ray Observatory was carried into low Earth orbit by the Space Shuttle Columbia. The observatory was deployed from the shuttle’s cargo bay at 155 miles above the Earth. Two firings of an attached Inertial Upper Stage rocket and several firings of its own on-board rocket motors after separating from the Inertial Upper Stage placed the observatory into its working orbit.

Unlike the Hubble Space Telescope’s circular orbit that is relatively close to the Earth, the Chandra X-ray Observatory was placed in a highly elliptical (oval-shaped) orbit. At its closest approach to Earth, the observatory will be at an altitude of about 6,000 miles. At its farthest, 86,400 miles, it travels almost one-third of the way to the Moon. Due to this elliptical orbit, the observatory circles the Earth every 64 hours, carrying it far outside the belts of radiation that surround our planet. This radiation, while harmless to life on Earth, can overwhelm the observatory’s sensitive instruments. The X-ray observatory is outside this radiation long enough to take 55 hours of uninterrupted observations during each orbit. During periods of interference from Earth’s radiation belts, scientific observations are not taken.