Astronomy Picture of the Day

Discover the cosmos! Each day we feature a different image or photograph of our fascinating universe, along with a brief explanation written by a professional astronomer.

January 2, 1996
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The X-Ray Sky
Credit: NASA, HEAO-1, Boldt (GSFC) and Garmire (Cal Tech/PSU), Skyview, Allen, Jahoda, Whitlock

Explanation: What if you could see X-rays? If you could, the night sky would be a strange and unfamiliar place. X-rays are about 1,000 times more energetic than visible light photons and are produced in violent and high temperature astrophysical environments. Instead of the familiar steady stars, the sky would seem to be filled with exotic binary star systems composed of white dwarfs, neutron stars, and black holes, along with flare stars, X-ray bursters, pulsars, supernova remnants and active galaxies. This X-ray image of the entire sky was constructed with Skyview, using data from the first High Energy Astronomy Observatory (HEAO 1), and plotted in a coordinate system centered on the galactic center with the north galactic pole at the top. Sources near the galactic center are seen to dominate in this false color map which shows regions of highest X-ray intensity in yellow. Astronomers' ability to observe the sky at X-ray energies will be greatly enhanced by the recently launched X-ray Timing Explorer (XTE) satellite.

Tomorrow's picture: The X-ray Timing Explorer

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Authors & editors: Robert Nemiroff (GMU) & Jerry Bonnell (USRA).
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