Comet P17/Holmes has either suffered an explosion or a large collision. The comet was just a very dim object as it passed the sun back on May 20. It was so dim that it could only be seen in a large observatory telescope. Then on Oct. 24 something very strange happened; the comet brightened to the point that it can be seen with the naked eye. It has increased in brightness a million times or more.
In a telescope you can see the tiny, little nucleus with a bright area fanning out from the nucleus and extending outward in the direction of its motion.
Around both of these areas is a large sphere that appears to be a cloud of dust, gas and debris from the comet. The spherical cloud is growing a little larger each night and is now larger than the planet Jupiter. I have observed it for the last four nights, taking many photographs. What happened to the comet is still being debated.
The comet's spherical cloud will get dimmer as it expands, and the comet will probably go back to being a dim comet as it journeys out to Jupiter and then starts its trip back around the sun again.
The comet has a revolutionary period of about 8 years, and in 1892 the same thing happened. The comet has made about 11 trips around the sun since the last collision or explosion.
The chance of two collisions in 11 trips around the sun is a bit too much, and you have to wonder whose driving this thing. It is more likely that some sort of explosion has occurred.
I did hear today that the comet seems to be trying to form a tail.
To locate the comet, look to the northeast and look upward four or five fists high and you will see the comet. A fist held at arm's length is about 10 degrees. Check out all the brighter visible stars in that area with your binoculars, and you will find a nice size blob of glowing dusty gas.
Jim Honeycutt teaches astronomy at Oxford College of Emory University.