Comet ISON, a rare type of comet from outside the solar system, has brightened "considerably" in recent days and could be on the cusp of visibility to the naked eye in the night sky, scientists say.
Scientists are calling on the astronomy community and amateur skywatchers to closely monitor the comet as it nears a close pass by the sun later this month. They want to see whether the comet continues to brighten, and what that could mean is happening to it.
Astronomers have been tracking ISON since last September, when scientists from Belarus and Russia who are part of an international collaboration called the International Scientific Optical Network spotted its faint impression on images captured by a telescope near Kislovodsk, Russia. It has been observed by the Hubble Space Telescope, recently by the Messenger spacecraft orbiting Mercury, and by amateur astronomers.
But it remains to be seen how bright the comet could appear from here on Earth. Some early projections suggested it could become a "comet of the century" that could shine nearly as brightly as the moon, though those expectations have been tempered significantly.
That the comet has brightened as it approaches the sun could be a sign that the comet is "turning on" and will continue to brighten as it nears its pass by the moon Nov. 28, according to an e-mail alert shared by EarthSky.org on Thursday. But it could also be a sign that the comet is breaking up, something that would mean there won't be much more of a show from here on Earth.
If it doesn't become bright enough to be seen with the naked eye, it could still be visible with binoculars if you don't have a telescope. The comet is currently hidden in the darkness of the eastern pre-dawn sky, according to EarthSky. It will be close to the bright star Spica on Sunday and Monday mornings.
At least one report has been made of the comet being visible with the naked eye, though, according to Sky & Telescope. As with all heavenly bodies in the night sky, Comet ISON is best seen from areas far from the light pollution of cities.