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 June 1
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X-Ray Wind From NGC 3783
Credit: PSU, NASA

Explanation: A black hole is supposed to inexorably attract matter. But the intense radiation generated as material swirls and plunges into its high gravity field also heats up surrounding gas and drives it away. In fact, measurements made using this recent Chandra Observatory X-ray spectrum of active galaxy NGC 3783 reveal a wind of highly ionized atoms blowing away from the galaxy's suspected central black hole at a million miles per hour. Displayed in false colour, the bright central spot is the X-ray image of NGC 3783 while the lines radiating away represent an X-ray spectrum of this source produced by Chandra's High Energy Transmission Grating (HETG). An X-ray spectrum is the analogue to the rainbow spread of colours in a visible light spectrum. It represents a detailed, spread out image of X-ray colours or energies arising from the source. Ionized atoms of iron, magnesium, oxygen, nitrogen and other elements produce patterns of absorption at known X-ray energies. These patterns have been identified in the spectrum of NGC 3783 at slightly shifted energies and the measured shifts indicate the hot wind's velocity.

Tomorrow's picture: Secret Spiral

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/GSFC
& Michigan Tech. U.