July 16, 2013, 9 a.m.
Sungrazing comets are a special class of comets that come very close to the sun at their nearest approach, a point called perihelion. To be considered a sungrazer, a comet needs to get within about 850,000 miles from the sun at perihelion. Many come even closer, even to within a few thousand miles. Being so close to the sun is very hard on comets for many reasons. They are subjected to a lot of solar radiation which boils off their water or other volatiles. The physical push of the radiation and the solar wind also helps form the tails. And as they get closer to the sun, the comets experience extremely strong tidal forces, or gravitational stress. In this hostile environment, many sungrazers do not survive their trip around the sun. Although they don s orbit suggests that it may gain enough momentum to escape the solar system entirely, and never return. Before it does so, it will pass within about 40 million miles from Earth on December 26th. Assuming it survives its trip around the sun. Short, narrated video about sungrazing comets.Watch this video on the NASAexplorer YouTube channel.For complete transcript, click here. For More InformationSee [http://www.nasa.gov/content/goddard/timeline-of-comet-ison-s-dangerous-journey/](http://www.nasa.gov/content/goddard/timeline-of-comet-ison-s-dangerous-journey/)
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