The Halloween Comet

Comet Holmes continues to amaze & stun astronomers world-wide

by Bill Georgevich

comet holmes motion in sky
Motion of the comet viewed from earth
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Comet Holmes, the comet that suddenly brightened nearly a million times on October 24, 2007, initially appeared as a new star in Perseus. That star has grown into a fainter but much larger fuzzy ball.

Based on orbital computations and luminosity before the 2007 outburst, the comet's nuclear diameter was estimated at 3.4 km. In late October 2007, the coma's diameter increased from 3.3 arcminutes to over 13 arcminutes, about half the diameter that the Moon subtends in the sky. At a distance of around 2 AU, this means that the true diameter of the coma swelled to over 1 million km, or about 70% of the diameter of the Sun. By comparison, the Moon is 380,000 km from Earth. Therefore, during the 2007 outburst of Comet Holmes, the coma was a sphere wider than the diameter of the Moon's orbit around Earth.

The comet has very little appearance of a tail because the position of Comet Holmes makes the tail stream directly behind it. As a result, the comet is not visible from Earth.

If you want to see the comet, don't wait because it will most likely continue to fade as it grows larger and larger. Soon the glare of the moon will wash out this Great Halloween Comet of 2007.

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comet holmes
Photo of the comet taken on November 11, 2007 by John Lanoue

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