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.

March 17, 1997
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Comet Hale-Bopp Over Val Parola Pass
A. Dimai (Col Druscie Obs.), AAC

Explanation: Comet Hale-Bopp is now much brighter than any surrounding stars. It can be seen even over bright city lights. Out away from city lights, however, it is putting on quite a spectacular show. Here Comet Hale-Bopp was photographed last week above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tale is created when fast moving particles from the solar wind strike recently expelled ions from the comet's nucleus. The white dust tail is composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Recent observations show that Comet Hale-Bopp's nucleus spins about once every 12 hours. Comet Hale-Bopp is now visible in both the early morning and early evening sky, and will continue to brighten this week.

Tomorrow's picture: X-Ray Pleiades

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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.