We're all familiar with the doomsday scenario of a comet impacting the earth. Both science and cinema suggest that bad things would happen. But what would happen if a comet hit the sun? As luck would have it, our own Amy Shira Teitel specializes in just this kind of cosmic conjecture. She's got the lowdown in today's DNews report.
Comets are basically giant blocks of rock and ice that, in our solar system anyway, trace elliptical orbits around the sun. As they approach, solar wind melts some of the ice and gives comets that spectacular tail.
Most comets orbit at a great distance, way out in the Oort Cloud, which is a good band name. Those that come in close to the sun are called sungrazers, which is also a good band name and is, in fact, taken. Sungrazers can pass within a few thousand miles of the sun's surface.
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That said, keep in mind that the sun doesn't really have a surface. It's really just a ball of extremely hot gases, mainly hydrogen. Comets that get too close run the risk of passing through the sun's Roche Limit, beyond which passersby tend to get ripped apart by gravitational forces. And that's just what happens to comets that are smaller or structurally weaker.
Stronger comets can survive this proximity and pass back out of the Roche Limit, but they still have other problems besides gravity. Get near enough to the sun and solar radiation -- the same stuff that gives us sunburns -- can be powerful enough to crack rocks apart.
A comet that's big and strong enough to head straight into the sun goes out with a serious bang. After accelerating to more than 370 miles per second, the comet is flattened by the sun's atmosphere, generating a fantastic explosion that throws out cosmic tidal waves of ultraviolet radiation and x-rays. These incidents are pretty spectacular -- check out this NASA footage -- but pose no threat to Earth.
-- Glenn McDonald
Space.com: Sungrazing Comets: How They Dive-Bomb the Sun
NewScientist: What Would Happen If a Massive Comet Crashed into the Sun?
NASA: Comet Lovejoy Plunges into the Sun and Survives