Credit: Max-Planck-Institut für extraterrestrische Physik & LETG Team

First Rainbow: CHANDRA'S Low Energy Grating

The low energy transmission grating (LETG) on the Chandra X-ray observatory is designed to split X-ray light into its component wavelengths (or colors) similar to the way water droplets in the atmosphere disperse sunlight into a rainbow. This lets astronomers study the makeup of the million degree gas surrounding stars, galaxies, black holes and other cosmic objects in detail. On Sunday, September 6, 1999 the LETG was placed in the beam of the CHANDRA mirrors for the first time, and for the first time detected X-rays from an astronomical object, the bright nearby star Capella. This "first rainbow" is shown in the image above. The bright "knots" are X-ray "emission lines" produced by excited atoms in the extremely hot gas in the corona which surrounds the surface of Capella. More than 100 emission lines could be detected in the whole spectrum. The LETG was developed by the Max-Planck-Institut für extraterrestrische Physik (MPE) in Garching together with the Space Research Organization Netherlands (SRON) in Utrecht.

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Page Author: Dr. Michael F. Corcoran
Last modified June 14, 2001