Comet Elenin is just passing through

A newly discovered comet will make its closest approach to Earth next week. Comet Elenin was claimed and named Dec. 10, 2010 by Russian amateur astronomer Leonid Elenin. (With a first name like that, the man was destined to be an astronomer.)

Comet Elenin should enter naked eye visibility (magnitude +6) when it comes within 22 million miles of Earth on Oct. 16. It won't look like much, so break out the binoculars or telescope and aim them east toward the morning sky between one and two hours before sunrise.

Discovering a comet is a practice of patience, but the process hasn't changed much since astronomy studies began. For a span of several nights, an observer charts a specific section of sky and searches for change among the fixed objects. If a "star" has shifted relative to the other stars and is determined through process of elimination not to be a planet or other known entity, it stands a pretty good chance of being an as-yet-undiscovered comet or meteor.

Elenin, which is around two to three miles in diameter, has met with the same fate as other comets that approach Earth - that is, being tagged in overblown proportions as a potential harbinger of doomsday. Theorists have suggested everything from a life-obliterating impact, nuclear winter and a repeat of what happened to the dinosaurs (in no particular order) as possible consequences of visiting comets.

There's nothing to worry about. Two images, one captured Aug. 19 and the other Sept. 6 during Elenin's journey toward the sun, show that it has dimmed. Comets tend to disintegrate as they approach the sun because of the amount of ice they contain. As pieces separate from the comet, they create dust trails in its wake, that, when crossed with Earth's orbit, create the meteor showers we love to watch.

Elenin's first journey into our inner solar system has not been gentle. The comet was hit by a coronal mass ejection (solar flare) Aug. 20, accelerating its disintegration shortly before its closest approach to the sun Sept. 10.

Assuming the comet stays intact, it will continue on back into space after it approaches Earth on Oct. 16. Its orbital period is long and eccentric (anywhere from 12,000 to 600,000 years), and its modest size and rate of disintegration means it likely won't survive long enough to make a return trip. In fact, the jury is still out on whether Elenin is a periodic comet at all.

SKY CALENDAR

Oct. 12 - Full moon.

Oct. 21, 22 - Orionids meteor shower.

Oct. 26 - New moon.

Oct. 29 - Jupiter at opposition and closest approach to Earth. Viewing its four largest moons will be possible with a good pair of binoculars.

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