Comet Holmes visible in Perseus

The comet was observed at about magnitude 14.5 since July and had showed signs of a slow fading; however, very early on the morning of October 24, Juan Antonio Henr’quez Santana (Spain) reported that the comet was much brighter than expected. This was all rapidly confirmed. One comet observer, Bob King (Minnesota, USA), made one of the confirming observations on October 24.17 and gave the magnitude as 7.1. He described it as appearing like a yellowish star. Interestingly, he reobserved the comet on October 24.47 and gave the magnitude as 4.0 with the naked eye!! Seiichi Yoshida (Japan) observed the comet on October 24.55 and gave the naked-eye magnitude as 3.5. Further observations by Yoshida gave the naked-eye magnitude as 3.0 on October 24.63 and 2.8 on October 24.72.

Source: Kronk’s Cometography

Via Chris Lintott’s Universe comes news that Comet Holmes is undergoing a massive outburst. The comet has been known since 1892, but it’s one of the solar system’s oddities. It takes seven years to travel around the Sun, coming as close as 2 AU, that’s twice the Earth-Sun distance, and wandering out as far as 5 AU, about as far away as Jupiter. Usually Comets get brighter when the pass the Sun. They heat up and ice and dust boils off making the coma and tail. This doesn’t really happen much to Comet Holmes. It tends to peak around Magnitude 15 or 16 which, despite being large numbers is very faint. Off the top of my head I think it would have to be 10,000 times brighter to be visible.

This is what has unexpectedly happened. The rise to Magnitude 2.8 (small numbers are brighter) makes it as visible as a lot of named stars. You should be able to see it in the northeastern sky in evening. Look for the W of Cassopeia and follow a line down to the horizon from the middle star. You can click on the map below to see it larger.

What is making it brighter? One guess would be an impact. The whole point of NASA’s Deep Impact mission was to smack into a comet to see what was kicked out. That’s unlikely in this case. Comet Holmes has a history of outbursts, so it would have to be a staggeringly unlucky comet to be hit so often. More likely is that the structure of the comet is unstable in some way causing outbursts as pockets of ice boil and bubble out of the surface. Why that should be so for this comet rather than others I couldn’t say.

If you’re interested in comets, Gary W. Kronk’s Cometography site should be your first stop.