Comet ISON is expected to make its closest approach to the sun on Thursday, Nov. 28. This also happens to be Thanksgiving day. On its trip around the sun, ISON will come within 730,000 miles of surface, but no one knows if it will come out on the other side in one piece. The comet could evaporate from extreme temperatures or be ripped apart by gravitational stresses.
Here’s what you need to know.
What is a comet?
Comets are typically made of ice, dust, and rock. When a comets gets close to the sun, the heat causes the ice to vaporize. The vaporizing gas takes the dust with it and forms a tail that can sometimes be seen from Earth. Comets tend to orbit the outer-edge of the solar system in the Oort Cloud or the Kupier belt, which is just beyond the orbit of Neptune.
When was was Comet ISON discovered?
ISON was discovered by a pair of Russian astronomers on Sept. 21, 2012 while it was still in the Oort Cloud at the outer-edge of the solar system, beyond the orbit of Jupiter.
What is the significance of ISON?
ISON has never been to the inner-edge of our solar system before. Since it comes from the very edge of the solar system (it’s been travelling for about 5.5 million years to reach us) it contains chunks of ice and rock from when our solar system was formed 4.5 billion years ago. This gives us a glimpse of what our solar system was like at its birth.
How big is Comet ISON?
When ISON was first detected, it was so bright that scientists thought it would be pretty big once it got closer to Earth. But the comets has been shedding some mass during its journey and is now relatively small, Jim Green, director of NASA’s planetary science division, told the Washington Post. Green estimates that ISON is around 1.2 miles wide now. In July, it was about triple that size.
What will happen to COMET ISON on Thanksgiving Day?
In a video for NASA, Don Yeomans, manager of the space agency’s Near-Earth Object Program, lays out three possible outcomes for Comet ISON when it rounds the sun on Nov. 28.
In the first and most exciting scenario, ISON could survive the passage of the sun and continue on as an active comet. At its closet approach to sun, the comet’s temperature will reach 5,000 degrees Fahrenheit, writes astronomer Matthew Knight on the CIOS blog. The extreme heat will cause much of the dust, rock, and ice on ISON’s surface to vaporize, producing a fairly bright tail that would be visible in the early morning sky. Viewers should also be able to see the comet during the first or second week of December.
In the second instance, the sun could break ISON apart in several large chunks. The break-up could happen at any time — before or after its closest approach to the sun. This could still produce a great show in early December, says Yeomans.
In the last scenario, ISON could completely fizzle. It would disintegrate into a cloud of dust, torn apart by sun’s intense gravity and heat. This is something that could happen at any time and would rule out the possibility of viewing the comet with the naked eye in December.
How can I view Comet ISON?
Astronomers and a fleet of NASA spacecraft have been watching ISON for the last several months, snapping incredible photos of its evolution.
Before dawn on Tuesday, Nov. 26, was the last chance to see Comet ISON before it rounds the sun, according to Space.com.
If the comet isn’t demolished, skywatchers should be able to see it with the naked eye or binoculars in the early morning sky during the first or second week of December.
Zolt Levay of Baltimore’s Space Telescope Science Institute told LiveScience: “The best locations to view Comet ISON would be any place dark, away from artificial lights, with clear sky, lower humidity and a low eastern horizon, with no trees, buildings or mountains in the way.”
Many national parks or beaches on the Atlantic Coast would provide unobstructed views.
NASA’s Solar Dynamics Observatory plans to post near realtime images of the comet as it grazes by the sun staring around 12:45 p.m. EST on Thanksgiving day.
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