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.

2001 March 14

Comet McNaught-Hartley
Credit & Copyright: Brian Lula

Explanation: Outbound and climbing above the plane of our solar system, comet McNaught-Hartley (C/1999 T1) is presently soaring through northern skies. This lovely picture, a composite of many 30 second exposures made through three color filters, records the delicate colors in its diminutive coma and tail in late February. Combining the exposures to produce the final image registered on the comet causes stars to appear as "dotted trails", evidence of the comet's motion relative to the distant stellar background. Discovered by southern hemisphere observers, this comet's closest approach to the Sun occurred in December last year as it passed just outside planet Earth's orbit. For now, the brightest comet in the sky, this primordial chunk of solar system is crossing from the constellation Hercules to Draco and will continue to fade from view. Never visible to the unaided eye, McNaught-Hartley is still at about 10th magnitude and can be viewed by comet seekers using small telescopes.

Tomorrow's picture: Photospheric Islands in the Stream

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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.