Guest Author - Lea Terry

Comets are some of the most elusive, but also eagerly anticipated, astronomical events. And Comet McNaught, making an appearance this week, is the brightest comet to visible from Earth in 40 years, according to the International Comet Quarterly at the Harvard-Smithsonian Center for Astrophysics.
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Comet McNaught was discovered in August 2006 by Australian astronomer Robert McNaught, and is the brightest comet since 1965, when Ikeya-Seki made its appearance. (Ikeya-Seki is the brightest comet to be visible from Earth since 1935.) Comet McNaught is even brighter than the much-publicized appearance of Hale-Bopp in 1995, and is bright enough to be seen during the daytime. However, daytime viewing can be tricky, as Comet McNaught is rounding the Sun, and skywatchers must be careful not to look directly at the Sun when in search of the comet. (To spot the comet, block the Sun with your hand, or find a nearby building that blocks its, and look just east of the Sun.)

So far, Comet McNaught hasn’t disappointed. As it veered into Mercury’s orbit, the comet ejected fiery debris, putting on a spectacular show visible in the daytime, with the naked eye. Astronomers assign a numerical value to celestial objects to denote their brightness; the lower the number, the brighter the object. Comet McNaught has reached minus 5, compared to minus 4 for the planet Venus, which shines brighter than any star, and minus 12.7 for the full moon.

Comet McNaught has been described as looking like an elongated cloud, and pointing up and to the left. It has been visible for approximately 30 minutes after sunset each night, in addition to several daytime appearances. In the United States, the comet has been easily visible everywhere from Hawaii to California to Utah. While residents of the Northern Hemisphere have had a clear view of the comet for the past several days, it is steadily heading south. Each day, the comet will move away from the Sun and farther south, giving residents of the Southern Hemisphere a viewing advantage. Comet enthusiasts can also watch the comet online, with several sites streaming live or near-live images, and others posting still images.