Obscure Comet Explodes Into View

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A comet that has orbited the Sun in obscurity since its discovery more than a century ago has suddenly turned into a showoff. In just two days, it grew almost a million times brighter -- from a blip far too faint to see without a good-sized telescope, to a fuzzy yellow ball that’s brighter than most of the stars that are visible to the naked eye.

Amateur astronomer John Gianforte snapped this picture of the rapidly expanding comet from his home observatory on October 30. It shows that the comet has expanded to the size of Jupiter, although most of its size consists of an extremely thin cloud of gas and solid particles expelled from the comet's body. (John Gianforte)

Comet Holmes is passing through the constellation Perseus, the hero, which is high in the northeast in early evening and passes almost directly overhead in the wee hours of the morning. The comet has not developed a tail, however, because it is too far from the Sun. As a result, it is difficult to distinguish from a true star. Binoculars or a small telescope reveal a bit of fuzziness around its edges.

From October 23 to 25, the comet’s brightness increased from 17th magnitude to 2nd or 3rd (a smaller number indicates a brighter source) -- a factor of one million -- but astronomers don’t know why.

	A November 13 view of the comet against the stars of Perseus. (John Gianforte)

It flared up at least once before, in 1892, when it was discovered by amateur astronomer Edwin Holmes. It disappeared from view the following year, and was seen only twice more until the 1960s. Other comets have flared up when pockets of gas exploded from beneath their icy crusts, or when the comets split into fragments. So far, there is no evidence that Comet Holmes has undergone either of these events. It is more than 150 million miles from Earth, and no more than a few miles in diameter, so it is difficult for astronomers to see any details.

Because of its erratic behavior, the comet could fade back into obscurity at any time. For now, it is in the sky all night, although it may be tough to see through the glare of the waning Moon. The view should improve as the Moon grows fainter, and rises later each night.