Comet Hyakutake

March 18, 1996

Dan Marcus of the Buffalo Astronomical Association called in early March to tell me that a comet first spotted on January 30 by Yuji Hyakutake will be visible through the remainder of this month and much of April. I appreciated his call as I have never seen a comet and hope finally to catch a glimpse of this one. My chances are good.

For amateur observers without access to a powerful telescope, the appearances of most recent comets have been busts. In particular, the much heralded return of Halleyπs Comet in 1987 produced only a dim blob, at its best barely visible to the naked eye. It was quite unlike that cometπs previous approach in 1910 when, after a spectacular display with its tail extending across a sixth of the sky, the tail actually swept through the earth. There were, of course, no terrestrial consequences, much to the chagrin of those who had been hoodwinked into purchasing asbestos suits for protection.

This Planet Hyakutake (aka C/1996 B2) wonπt be that sensational, but it will be easily visible to the naked eye. Dan had already seen it through seven power binoculars when he called and he said that it is predicted to reach magnitude one or even less as it makes its way across the heavens. That is a very bright celestial object.

Magnitude is the astronomerπs measure of brightness and the lower the number, the brighter the display. To give you some sense of that scale, consider the magnitude of a few familiar stars: Polaris (the pole star) 2.0, the dimmest star in its constellation, the Little Dipper, 5.5; the stars in the Big Dipper ranging from 1.8 to 3.3. Thus this comet will at times be brighter than any of those easily observable stars.

There are of course a few brighter. The three brightest stars in the evening sky during this period, all near the horizon, are Arcturus, Vega and Capella, each about zero magnitude. Several planets even have negative magnitudes, Venus the brightest at -3.9, but they are below the horizon now.

This comet will be reasonably bright, but will you be able to find it? Happily, the answer to that question, even for those who know very little about the night sky, is yes. From March 25 to 27 Comet Hyakutake will pass between the Big and Little Dippers. By that time its brightness should have increased so that it will be as bright as any star in those constellations. Thus all you need to do is to find those easily identifiable star groups and look for an additional bright but hazy spot between them.

If you also know one other constellation, you can determine the rest of the cometπs path. Cassiopeia is a W-shaped star group that is easily located. Find it the same distance the other side of Polaris from the handle stars in the Big Dipper. Comet Hyakutake will pass near Cassiopeia and a line across the heavens between the two Dippers and near Cassiopeia will give you its full route. (For more knowledgeable observers, the comet is already approaching Arcturus as it moves toward the Dippers.) Once you find it, you should be able to relocate this comet each night as it speeds toward its snap-the-whip pass around the sun.

If you look very closely, especially with binoculars, you may also see a long but dim tail at different times in the cometπs trip through our solar system.

And if my luck holds and clouds intervene, weπll have another chance next year when Comet Hale-Bopp will arrive.