Picture of the Moment...

Comet 17P Holmes, the exploding comet, 31 October 2007

Comet 17P/Holmes exploded on 25 October 2007, sending a cloud of debris into space and increasing it's brightness by a million times. This transformed it from an object requiring a large telescope to see into a second magnitude star, rivalling those in its host constellation - Perseus.


Comet Holmes, thr Pleiades & the Moon

Images 1 to 3 of the above montage show Holmes, the Pleiades star cluster and the Moon all photographed at the same scale on the same night. The 4th picture is a larger view of the comet on the same evening, 31 October 2007.


As the cloud expanded around 2km per second so it came to look less like a star and more like a comet. Because of the great distance of around 200 million km, the expansion was too slow to watch in real time but was quite evident from night to night.

The cause of the explosion is unclear, though the most likely explanations are a collapsing void in the nucleus as it evaporated due to heating by the sun or a collision with companion piece of nucleus . This is the second recorded such event on Holmes, the first in 1892 being the one that lead to the comet's discovery.

Click the image or here for more of the story and to see how the comet grew in the following weeks.


Picture added on 30 Nov 2007

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