Astronomical society teams with library for comet viewing

After the excitement of an asteroid passing near earth last week and a meteorite crashing down in Russia, earthlings will get a chance to view a comet in March that scientists are predicting should be visible with the naked eye, despite being 100 million miles away.

The Westminster Astronomical Society Inc. and the Carroll County Public Library are teaming up to offer a program at 7 p.m. March 11 at all library branches to help the public find and view the comet.

The comet, named Pan-STARRS, was discovered in June 2011 by the Panoramic Survey Telescope and Rapid Response System atop the Haleakala volcano in Hawaii, according to NASA. It originates from the Oort Cloud, which is known for producing both spectacular comets and disappointing failures, according to NASA's web site.

The Oort Cloud is theorized to surround our solar system in a spherical "halo" that may be a large as half to a full light-year in radius, said Christian Ready, a member of the Westminster Astronomical Society.

Because of their distance, comets are very cold, thus the term "dirty snowball" is sometimes used to describe them, he said.

"Occasionally one of the comets' orbits gets thrown off, for reasons we don't fully yet understand, though it could be due to undiscovered dwarf planets way out there, and the comet 'falls' toward the sun," Ready wrote in an email.

Pan-STARRS will be making its first pass around the sun during this orbit, which means it is likely to be brighter than older comets because it will still be covered in volatiles, like ices filled with dust, said Curtis Roelle, of the Westminster Astronomical Society.

The sun causes the ices to melt or sublimate, which leads to the visible tail that helps distinguish a comet from other bodies in the sky. Comets can even have two tails, he said.

"The gas tail is usually straighter and the dust tail is usually more curved, because the dust particles are moving more slow," Roelle said.

Originally, Pan-STARRS was expected to be a brightness of magnitude 1, Roelle said, which means it would be as bright as a planet, like Mars. Since then, scientists have downgraded it to a magnitude 3, which is less bright.

"It would be as bright as a star if its light was all in one pinpoint, but it's not, it is divided among the comet and its one or two tails," Roelle said.

As a frame of reference, the stars in the Big Dipper constellation are a magnitude 2, he said, and a magnitude 3 is about half as bright.

"It's recommended that people bring binoculars because it's not as bright as expected, which is often the case with comets," he said.

The Westminster Astronomical Society will also be providing telescopes at the libraries, he said, but binoculars will probably be more useful since the comet will be visible pretty low in the sky, near the earth's horizon.

"It's going to be sinking almost immediately," Roelle said, so he recommends that people get to the library for viewing as close to 7 p.m. as possible.

For those who can't make it, the comet should be visible at twilight at least through March 24, as long as you know where in the sky to look.

Lisa Back, spokeswoman for the library, said the library has partnered with the Westminster Astronomical Society on many astronomy-themed events.

"The presenters from the group do a wonderful job of making astronomical ideas easy for viewers of all ages to understand and enjoy," Back wrote in an email.

One collaboration for last year was the viewing of the Transit of Venus, which occurred last summer.

"We probably had about 100 people viewing the unique occurrence at each of our six branches that day," she said.

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