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.

September 10, 1996

M77: Spiral with a Strange Glow
Credit: UIT, NASA

Explanation: Why is M77 surrounded by an ultraviolet glow? M77, also called NGC 1068, appears at first sight to be a relatively normal barred spiral galaxy. But when photographed in the ultraviolet (UV), as shown above in false colour, the galaxy sports an ultraviolet halo - shown as violet in the photograph. The blue spiral structure closer to the picture's centre indicates normal ultraviolet emission from bright young stars that have recently formed there. Astronomers now hypothesize that the outer glow arises from UV light emitted from the galaxy's active centre and reflected to us from clouds of gas and dust. These same gas and dust clouds obscure the active centre of this Seyfert galaxy - where an ultramassive black hole is thought to live.

Tomorrow's picture: In the Centre of Spiral M77

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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.