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Comet Pan-STARRS to pass over Western skies

Tue., March 5, 2013, midnight

Recently discovered comet on course to pass over Western skies

A comet streaking through our solar system will be visible from across the Inland Northwest over the next few weeks.

A telescope in Hawaii discovered Comet Pan-STARRS in 2011. It is the first of three comets expected to pass near Earth this year.

Sky watchers will be able to see the comet just above the setting sun. As of last week it was visible to the naked eye from the southern hemisphere.

On Thursday, Pan-STARRS is going to be only a few degrees above the horizon about a half hour after sunset. It will make its closest pass of the sun on Sunday.

By next Tuesday, it should be about eight degrees above the horizon after sunset and located just to the left of the sliver of a new moon.

From there it will remain in the western sky, moving slightly northward each day, reaching its highest point in the sky on March 20.

“I hope it is as bright as they say it is going to be,” said Jerry Eber, vice president of the Spokane Astronomical Society. “If we have a clear evening, we should be able to see it.”

Pan-STARRS is named for the acronym of the Panoramic Survey Telescope and Rapid Response System in Hawaii.

The comet is believed to have originated in the Oort Cloud, a spherical outer boundary area of the solar system that is theorized to contain billions of comets composed of dust, ice, methane and ammonia.

Frozen gases in comets are released as they approach the sun, creating the distinctive coma and tail formations typical of comets.

The Oort Cloud, which has never been observed but is accepted as a scientific reality, is so far from the sun that other stars can cause changes in orbital paths of the comets, sending some of them inward toward the sun on exaggerated elliptical orbits.

Many of the comets, including Pan-STARRS, are believed to be on their first encounters with the inner solar system. Their brightness is notoriously unpredictable, astronomers said.

The other comets that may be seen later this year include Comet Lemmon, now visible in the Southern Hemisphere and set to arrive in Northern skies in April.

Comet ISON has a potential to become one of the brightest comets ever seen. Its nucleus is estimated to be 1 to 10 kilometers in diameter, which is large for a comet. Astronomers speculate that ISON could surpass the visual displays of Comet Hale-Bopp in 1997 and Comet McNaught in 2007.

Comet ISON is named after a Russian telescope of the International Scientific Optical Network.

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