Astronomy Picture of the Day

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

2000 November 9
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

The Cosmic X-Ray Background
Credit: G. Hasinger (AIP) et al., XMM-Newton, ESA

Explanation: Early on, x-ray satellites revealed a surprising cosmic background glow of x-rays and astronomers have struggled to understand its origin. Now, peering through a hole in the obscuring gas and dust of our own Milky Way Galaxy, the powerful orbiting XMM-Newton telescope has recorded this deep image of the x-ray sky, resolving some of the mysterious background into many faint individual sources. The tantalizing image is color-coded, with red representing relatively low energy x-rays, photons with 500 or so times the energy of visible light. Green and blue colors correspond to increasingly energetic x-rays with up to about 10,000 times visible light energies. Notably, the faint sources tend to be green and blue, showing x-ray characteristics of huge amounts of material falling into massive black holes in very distant galaxies. Do massive black holes reside in the hearts of all large galaxies? The XMM-Newton results add to the growing consensus that they do and that, from across the universe, x-rays produced as matter feeds these black holes account for the cosmic x-ray background.

Tomorrow's picture: Cygnus A

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
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& Michigan Tech. U.