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.

April 17, 1996

NGC 7293: The Helix Nebula
Credit: Anglo-Australian Telescope photograph by David Malin
Copyright: Anglo-Australian Telescope Board

Explanation: The Helix nebula (New General Catalogue number 7293) is estimated to be a mere 450 light-years from the Sun, in the direction of the constellation Aquarius. At that distance it may well be the closest planetary nebula, offering a dramatic snapshot of a brief final evolutionary stage in the life of a solar-type star. In this colour image the nebula glows red in the light of nitrogen and hydrogen atoms energized by the ultraviolet radiation from the central star. The main rings themselves, though faint, have an angular size about half that of the full moon and span about 1.5 light-years. Because it is so close, it is a prime subject for study by astronomers. When the Hubble Space Telescope was focused near the inner edge of the main ring, at about the 12 o'clock position in the above image, it resolved some of the spoke like radial structures visible into intriguing cometary knots.

Tomorrow's picture: Hyakutake, Venus, Orion, and Pond

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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.