Kreutz Comet Orbits

A comet s Goddard Space Flight Center in Greenbelt, Md. created this short movie showing how the sun can cook a comet. Such a journey is currently being made by Comet ISON. It began its trip from the Oort cloud region of our solar system and is now traveling toward the sun. The comet will reach its closest approach to the sun on Thanksgiving Day — Nov. 28, 2013 — skimming just 730,000 miles above the sun’s surface. If it comes around the sun without breaking up, the comet will be visible in the Northern Hemisphere with the naked eye, and from what we see now, ISON is predicted to be a particularly bright and beautiful comet. Even if the comet does not survive, tracking its journey will help scientists understand what the comet is made of, how it reacts to its environment, and what this explains about the origins of the solar system. Closer to the sun, watching how the comet and its tail interact with the vast solar atmosphere can teach scientists more about the sun itself. Watch this video on the Goddard YouTube channel.

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/)

Before 1979, there were less than a dozen known sungrazing comets. As of December 2012, we know of 2,500. Why did this number increase? With solar observatories like SOHO, STEREO, and SDO, we have not only better means of viewing the sun, but also the comets that approach it. SOHO allows us to see smaller, fainter comets closer to the sun than we have ever been able to see before. Even though many of these comets do not survive their journey past the sun, they survive long enough to be observed, and be added to our record of sungrazing comets. Why are we seeing so many sungrazing comets?