Many of you are probably aware of the arrival of Comet McNaught. Here's a shot of the comet at sunset in Seattle on Thursday January 11th, taken from my office with my crappy digital camera:
(Also note the view, and understand why I am not in danger of taking up residence in California with the rest of the CV crowd anytime soon.) The comet is to the left of the street light, about 1/3 of the way from the right of the image, as you can see in this close-up:
It's a stubby sort of comet, and not particularly dramatic compared to Comet Hyakutake
, whose tail stretched a significant fraction of the way across the sky
. I was at an observatory in Chile when that one was up, with nice dark skies. Absolutely spectacular. While Comet McNaught is not much to look at in my crappy digital photo, it's amazing one can see it at all. As the photo shows, the comet is sitting right on the western horizon, which implies that it's close to the Sun. However, it's difficult for such objects to be seen, since light scattered from the Sun swamps all but the brightest objects. In other words, you can't see stars in the day time (especially in a well-lit metropolis like Seattle). The fact that we can see Comet McNaught means that it must be very bright indeed. (Note that overcoming the difficulty seeing stars in the daytime was at the root of Eddington's 1919 test of General Relativity. The idea was to search for the deflection of stars' positions by the mass of the Sun. However, you can't see stars when they're close to the Sun. Unless there's a total eclipse. Which there was in 1919. Clever.) On the other hand, McNaught's brightness is not unrelated to its location. Solar radiation (made of photons and charged particles) is responsible for producing the tail, so when a comet approaches the Sun, the flux of solar particles increases, and the tail becomes brighter. Also contributing to Comet McNaught's brightness is that it's probably making its first and only trip into the solar system -- McNaught's orbit is parabolic, indicating that the comet is not gravitationally bound to the solar system, unlike bound, repeating comets like Halley. McNaught probably started out in the extended cloud of debris left over from the formation of the solar system (known as the Oort cloud -- yup, same Oort
), and was then kicked into the inner solar system by an interaction with something else. Since McNaught is taking its first trip in, it had plenty of material left for setting off a nice juicy tail. However, when finished, it will fling right back out into interstellar space, never to be seen again. Now, while all of the above is impressive, the most impressive thing about Comet McNaught was that I spent a week at a meeting of several thousand professional astronomers right before this picture was taken, and nobody mentioned it! Nobody! I wandered out of a colloquium with some of my collaborators, and bumped into a UW astronomy undergrad clutching a pair of binoculars. He said "Hey! If you come over here you can see the comet!", and my collaborators and I looked back and forth at each other and said "What comet?" like a bunch of dumbasses. Now that's an impressive display of academic buffoonery. P.S. I hope I don't get kicked off for saying "dumbasses".
