On October 24, astronomers were astonished to see a comet that they had been observing since July grow in brightness until it was visible to the naked eye! Still visible, and likely to be visible without a telescope or any other aid for another few weeks, the comet 17P/Holmes appears to be exploding. A cloud of dust and gas around the comet makes it look similar to a nebulous star when seen through a telescope, and makes it look bigger and brighter to the naked eye.

Scientists speculate that the expansion may be due to a series of sinkholes in the comet’s nucleus—an implosion that then exposed ice in the comet’s interior to the effect of the sun, turning it to gas.
First discovered by E. Holmes in 1892 at a period when the comet was undergoing a similar type of expansion, comet 17P/Holmes has reappeared periodically, in spite of being lost several times due to improper calculations of its path. In 1964, accurate predictions were finally made with the help of computers, and the comet has been observed regularly since then.

Comet 17P/Holmes can be seen in the northern sky, just after sunset, in the constellation Perseus. It looks about as bright as the stars in the Big Dipper. This video further explains where to look, and what it looks like.