These images of Comet ISON were taken by NASA's Hubble Space Telescope on April 10, 2013, when the comet was 386 million miles from the sun. The image at right has been computer-processed to reveal the structure of ISON's inner coma. About 10,000 years ago, Comet ISON left our solar system's distant shell, a region known as the Oort cloud, and began streaking toward the sun. This November, the icy wanderer will reach the climax of its journey, potentially providing a stunning skywatching show here on Earth. Comet ISON[/img] was discovered just last September by two Russian amateur astronomers. Scientists have since recognized ISON as a possible "comet of the century," but to live up to its promise, it will have to survive its dangerous perihelion, or closest approach to the sun. ISON is what's known as a sungrazing comet. These suicidal objects have orbits that bring them within 850,000 miles of the sun, and scientists estimate that ISON's closest pass will be about 730,000 miles above the surface of Earth's star. [Photos of Comet ISON: A Potentially Great Comet] Sometime this month or perhaps in August, ISON is set to cross what's called the frost line. At this boundary, which lies some 230 million to 280 million miles from the sun, our star's radiation will start taking its toll on the comet, driving off more of its water and making ISON appear brighter. ISON's road will only get rockier from there. After the comet flies by Mars in October and then Mercury in mid-November, intensifying solar radiation will boil more material off ISON; pressure from solar particles could break the comet into pieces; tidal forces will create great gravitational stress; and one ill-timed solar storm could rip the comet's tail right off. Read more: http://www.foxnews.com/science/2013/07/18/comet-century-comet-ison-faces-risky-road/#ixzz2ZRT5iA7s
