Jimmy Westlake's Celestial News column appears Tuesdays in the Steamboat Today.
Find more columns by Westlake here.
Did you get to see Halley's Comet when it sailed past Earth in 1986? If not, you'll have to wait until 2062 for another chance to see it, because Halley's Comet requires 76 years to orbit the sun. In the meantime, you can watch tiny pieces of Halley's Comet rain down into the Earth's atmosphere every May and October during the annual Aquarid and Orionid meteor showers.
Comets are like big, dirty snowballs, more than anything else, which spend most of their time lurking in the cold recesses of the outer solar system. But every so often, a comet is pulled into the warm inner solar system by the gravity of the sun. As the snowball approaches the sun, the solar heat vaporizes the top layers of ice, releasing myriad dust particles that were trapped in the ice. The force of the solar wind blows the gaseous vapors away from the snowball, forming the comet's beautiful flowing tail and filling the comet's path with dust. With each pass around the sun, the comet sheds millions of little dust specks that remain behind in the comet's orbit and form a dusty river in space.
The Earth crosses Halley's dust river twice each year, once May 5 and again Oct. 21. When the dust particles plow into the Earth's upper atmosphere at nearly 150,000 miles per hour, they burn up in a brief but brilliant flash of light called a meteor. The dust specks are so small that you could easily hold 1,000 of them in the cupped palm of your hand.
This year's May Aquarid meteor shower will be especially favorable for folks living in the Western Hemisphere, especially the United States. In the hours between midnight and dawn on the morning of May 5, a single observer with dark, clear skies might see from 30 to 60 meteors, or, "falling stars," each hour. The new moon occurs May 5, too, so it won't interfere with meteor watching at all.
The May meteors from Halley's Comet seem to fan out from the stars in the constellation of Aquarius and, so, are called Aquarid meteors. You'll see the Aquarid meteors in all parts of the sky, but they all trace back to a common origin in Aquarius, high in the southeastern sky about 4 a.m. The closer to dawn you are, the more meteors you likely will see. And, although the peak of the meteor activity falls on the morning of May 5, you can still see plenty of Aquarid meteors on the mornings of May 4 and 6, as well.
Consider this a warm-up for 2062 when Halley's Comet reappears in person.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the Web sites of CNN.com, NASA's "Astronomy Picture of the Day" Web site, Spaceweather.com, Space.com, Discover.com, MSNBC.com, NationalGeographic.com, and in Sky & Telescope, Astronomy, Night Sky, Discover and WeatherWise magazines. His "Celestial News" article appears weekly in the Steamboat Pilot & Today. His "Cosmic Moment" radio spots can be heard on local radio station KFMU. Also, check out Jimmy's Web site at www.jwestlake.com.