Just yesterday, we reported on NASA’s use of “Solar Grazing Comets” to study the magnetic field of our Sun. But today, I want to talk about another SGC that has a lot of people in the space community very, very excited.
No, it doesn’t look like much right now. But that’s because ISON is very far away from the Sun. Once it gets closer and the Sun’s heat begins to create the atmosphere around the comet that creates the glow and tail we all generally know comets to have, then we’re going to see something amazing. We will hopefully see a comet that outshines the moon for at least an evening or two.
Because astronomers believe that ISON’s composition is similar to that of a comet that passed in 1680 and was reported to have been as bright. How do they know what the composition of the comet from 1680 was? Well, I don’t have the foggiest notion, and neither do most of the reports I’m reading.
However, most comets including this one are believed to come from the Oort Cloud, a hypothesized haze of ice and rock nearly a lightyear away from our Sun and a quarter of the distance between our Sun and our nearest neighboring star, Alpha Centauri. It is believed to be composed of the last snowy bits of material that formed our solar system and exists at the hypothetical edge of our Sun’s gravitational pull.
Astronomers predict that ISON will make its presence known in the night sky around October of this year. The moon-dimming display depends on a couple of things, however. Since heating up a ball of space snow has about as much chance of breaking it apart in space as it would on Earth, there’s every chance that ISON may just fracture into a bunch of smaller comets. Secondly, the comet has to come close enough to the Sun to create a tail, but not so close that it just gets disintegrated altogether. The current estimate is that ISON will pass within 800,000 miles of the Sun. That’s about 100 times closer to the Sun than the Earth. Mercury, by contrast, is about 36,000,000 miles from the Sun.
One interesting and unique ripple in this story is the fact that our Mars Curiosity and Mars Orbiter should be in a position to give us close up views of ISON’s passage before we get good views here on Earth. Imagine that? Pictures of a comet passing another world, then seeing it pass ours.