Monday, November 18, 2013

Comet ISON starts to brighten, astronomers begin to hope for a show

Astronomers on the ground and more spacecraft than ever before in history have been keeping a watchful eye on Comet ISON as it makes its way perilously close to the sun.
The 3- to 4-mile-diameter chunk of ice and rock has spent more than 4 billion years in the frozen depths of space, and on Thanksgiving, it will get so close to the sun that it will reach 5,000 degrees — hot enough to melt iron, said Seth Jarvis, director of Clark Planetarium.
In fact, it will get so close to the sun that it will be subject to the powerful tidal forces emitted by the star, and the comet’s nucleus could be torn apart.
ISON began brightening significantly late last week, and if that trend continues, it could make for a sight visible with the naked eye in the low east-southeast horizon in the pre-dawn sky and could last through mid-January. If the comet is torn apart, though, a best-case scenario would be a bright flash visible to Earth, and then nothing more.
"It’s rare that we see a sun grazer that’s significant enough in size that it has a good probability it will survive," Jarvis said. "But that’s the cool stuff, that we’re not sure what’s going to happen." Read More