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 14, 1997
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Hale-Bopp's Hoods
J. A. DeYoung (USNO). 61-cm Telescope, Washington, DC

Explanation: Comet Hale-Bopp is spinning. The nucleus of the comet is a dirty snowball about 25 miles in diameter that spins about once every 12 hours. As Comet Hale-Bopp spins, parts of the comet's surface shoot away in jets. Ejected material therefore makes rings, which appear in above photograph as "hoods" in the coma. Even though the central part of Comet Hale-Bopp's coma is quite condensed, the nucleus is not visible. Comet Hale-Bopp is now headed south, away from the Sun, and is getting dimmer. At its brightest last week, it was even brighter than Comet Hyakutake was last year, although with a less prominent tail. Comet Hale-Bopp will still be easily visible to northern observers for several weeks in the northwest sky after sunset.

Tomorrow's picture: Hale-Bopp and the Plateau de Bure Interferometer

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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.