Comet may be visible from Earth if it survives sun’s heat, gravity

The Comet ISON is pictured in this handout image from a November 25, 2013 footage from the STEREO-A spacecraft's Heliospheric Imager by NASA

A comet that left the outer edge of the solar system more than 5.5 million years ago will pass close by the sun on Thursday, becoming visible in Earth's skies in the next week or two - if it survives.

"There are three possibilities when this comet rounds the sun," Donald Yeomans, manager of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., said in an interview posted on NASA's website.