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December 06, 2013
CONTACT: K.E. Schwab

Comet ISON fizzles out

SLIPPERY ROCK, Pa. - Like Icarus of Greek mythology, Comet ISON, the latest deep space comet traveling in earth's solar system, has discovered flying too near the sun can be extremely hazardous.

"It was a bust," said Krishna Mukherjee, Slippery Rock University assistant professor of physics and pre-engineering, said, after tracking the once-in-a-lifetime comet as it streaked toward deep outer space - passed near the sun on its billions-of-years-old path.

"In the past months, the comet had baffled observers; once it would brighten then dim and again increase its brightness," she said. "Variation in brightness results in different materials boiling off the comet at different temperatures as the comet approaches the sun. Analyzing this information offered clues to the composition of this comet, which is composed of material available when the solar system was at its infancy. These sun-grazing comets often do not survive a close encounter with the sun. Astronomers can predict the path of a comet but not its fate - hence the drama."

The nucleus of a comet, which grew in public attention over the recent Thanksgiving holiday, she said, was mostly rock and ice. As a comet approaches the sun the sun's heat causes its ice to sublimate or vaporize and form a large cloud called "the coma," Mukherjee said.

"This is when the comet becomes bright. As it nears the sun the solar wind pushes back on the gases and creates what we see as the tail. It was way back in the 1950s scientists discovered the solar wind by observing that comets possess tails that are pointing away from the sun. In general a comet has two tails - one made of dust and the other of charged particles," she said.

"Every comet that passes near the Earth's sun, loses some of its material. It is dependent on how big it is initially and how close it actually comes to the sun," she said. "The nucleus of ISON was only a half-mile wide," so it was not extremely large," she said.

"If a comet is totally disintegrated the cometary debris still orbits the sun and if the earth happens to pass through that debris we on earth observe a meteor shower," she said.

"We had hoped the comet would survive, thus providing a spectacular tail away from the sun that would be visible from earth to the naked eye for several days," she said. "I had hoped to set up our telescope and give students the chance to see it, but now that it has emerged early this week as a extremely dim object from the far side of the sun it would be impossible to see," Mukerjee said.

"So from that standpoint, it was a bust," she said. Not only were my 'Space Science' students following the fate of the comet, but this semester I taught students from the Institute for Learning in Retirement and they were eagerly waiting to see the comet. But in the days and weeks after the initial disappointment I am hoping we will learn a lot from data analysis of a fleet of telescopes both in space and on earth that have been imaging the comet. Close encounters with the sun, such as this, gives us an opportunity to study the sun's magnetic field," she said.

Scientists believe that Comet ISON disintegrated into small particles and probably only a tiny portion of the nucleus remains as it passed the sun's surface. It is estimated the comet came within one-million miles of the sun's surface.

"Keep in mind this comet came from deep, deep space," Mukherjee said. "Think of our Voyager unmanned space probes. They were launched in 1977 to study Jupiter and Saturn, then continued on to explore other regions of space and became interstellar objects just last year after reaching the far edge of earth's solar system. ISON came from further out than that," she said.

Some had expected ISON to become a spectacular celestial light show throughout December if it survived its encounter with earth's sun. "ISON came from the Oort cloud that is about 4 trillion miles away from the sun. It is about 50,000 times the distance between the sun and earth, Mukerjee said.

Visitors from the furthest corner of our solar system are rare events hence the added interest, she said, "Such was not the case. Some had said it had the potential to provide the most spectacular light show in centuries."

"It was a turkey," Mukherjee joked, noting the comet reached its closet location to the sun on Thanksgiving, the traditional day for turkey dinners in America. Initially, some feared ISON had entirely vaporized behind the sun, but later reports show it just dramatically shrunk in size and Mukherjee says its nucleus, though much diminished in size, will now continue on its path reaching well-outside Earth's solar system as part of its natural orbit.

The comet was only discovered about a year ago, despite having be on its voyage for millions of years. Expert estimate there are still several trillion other comets - many with similar potential.

Mukherjee said she had followed ISON on NASA's website, including the SOHO project - the Solar and Helioscpheric Observatory - a cooperative effort between the European Space Agency and NASA. SOHO, launched in 1995, was designed to study the internal structure of the Sun, its extensive outer atmosphere and the origin of the solar wind, the stream of highly ionized gas that blows continuously outward through the solar system.

"In taking photos, SOHO is able to block out the intense light from the sun and still provide pictures, so it was interesting to watch the comet," Mukherjee said.

"There is currently another comet that people can watch with their naked eye. Comet C2013 R1 Lovejoy or in short 'comet Lovejoy,' named after its discoverer, can be seen in the northeastern horizon approximately two hours before sunrise, traveling from star Beta in the constellation of Bootes to the star Zeta in the constellation of Hercules. For amateurs it will be moving perpendicular to the horizon between the two bright stars Vega and Arcturus. As it moves away from the earth is will be diming rapidly; watch through binoculars or a small telescope between now and Dec. 15," Mukerjee said.

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