Comet Holmes brightens suddenly

On the 24th October, astronomers witnessed the unexpected brightening of Comet 17P/Holmes. A few days ago the comet was very dim and could only be seen with a very large telescope. However, on the 24th it experienced a sudden outburst and now appears a million times brighter. Scientists are not sure what has caused this outburst, but history tells us that the comet underwent a similar episode back in 1892, after which it stayed bright for another 3 weeks. There is no guarantee that Comet Holmes will do the same thing this time, but no doubt lots of budding astronomers around the world will be watching to see what happens.

Image of Comet Holmes
Recent image of Comet Holmes after its outburst - Credit: Chris Schur

Initial reports suggest that the comet looks more like a fuzzy star (see above) because there is no cometary tail. That said, it may yet grow one following the outburst. If you are quick, you can look for Comet Holmes in the constellation of Perseus using the finder chart below. At this time of year Perseus remains above the horizon throughout the night, but with the Moon being close to full phase at the moment, you will need a pair of binoculars or small telescope to clearly see the comets fuzzy appearance.

Finder chart for Comet Holmes
Stellarium image showing the location of Comet Holmes from UK at 8pm on the 25/10/07

You can think of comets as great dirty snowballs that hurtle around the solar system in stretched-out oval orbits around the Sun. Those that get too close find material on their surfaces being evaporated (turned into gas) by the immense heat of the Sun. The water vapour and dust released is usually blown away by Sun's rays to form an enormous tail that stretches out behind the comet. Comet Holmes orbits the Sun once every seven years at a maximum distance of 322 million km (200 million miles). It may be a new crack in this small chunk of ice that is causing it to look more reflective.