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View Full Version : The Vulcanids, a new sungrazer group



planetaryscience
2017-Feb-11, 10:15 PM
Some of you may be aware of the existence of the Kreutz Sungrazers, a gigantic group of comets broken up from the Great Comet of 1106, and the comet of 371 BC before that. Even more than 2000 years later, small fragments flying by the Sun have made up more than three quarters of every comet discovered. But I'm not here to talk about that group.

Late last December, I had just gotten Universe Sandbox and was messing around/testing with inputting orbits, and I was putting in the orbits of several objects with small perihelia (closest point to the Sun) to see how well the Solar Wind was simulated, when I began to notice something interesting. Although it wasn't easily visible based on their orbital elements, there was a definite clustering in the directions of their orbits. Here's a picture of what the orbits looked like to see for yourself: http://i.imgur.com/aqbgMsm.jpg

Well even more than a month later, quite a bit still remains uncertain, so most of what follows isn't final. I began investigating the individual objects, seeing if it could have just been a convenient coincidence that they appeared so close. Soon I was proven wrong, finding that the chances that the longitude of perihelion (the direction their orbit faced) and their semimajor axis (average distance from the Sun) would align so closely are less than 0.1% (and maybe even as low as 0.024%!) Unfortunately, that's as far as I've been able to tell for certain. The orbits of all of the asteroids except for 2 are very poorly known, but running the orbit of the 2 well-known objects back shows no significant change up to 20,000 years ago. As a result, it's difficult to say just how old this group is, but it is definitely more than 20,000 years old, and probably at least 100,000 years old. Based on the current orbits, here's what I think happened to this group, though:

At least 20,000 years ago, probably longer, a large (>20 kilometer) comet orbited in the inner Solar System, specifically being a Jupiter-Family comet, meaning that its orbit was mostly gravitationally affected by Jupiter. Eventually, Jupiter slowly nudged it into an orbit passing closer and closer to the Sun, making the comet burn its icy and rocky parts faster. Soon enough, the remaining hard chunks of iron and rock began to break off from one another, leaving the small fragments we see now. The individual asteroids have slowly began to move inward, moving out of Jupiter's gravity, leaving them on the orbit they are now, with 6 known small asteroids ranging between less than 100 meters across, to around a kilometer or larger. As they number among the 19 asteroids that get closest to the Sun (less than 12% of the Earth's distance from the Sun), I've informally named them The Vulcanids, after the tiny planet Vulcan that some astronomers thought orbited inside the orbit of Mercury in the mid-1800s (which, of course, turned out to be wrong!)

A paper is underway to announce it, and I hope should be published later this month.

Roger E. Moore
2017-Feb-11, 11:18 PM
Holy cow! I never thought they were going to find any! YAY!

https://en.wikipedia.org/wiki/Vulcanoid

:)

planetaryscience
2017-Feb-11, 11:36 PM
Holy cow! I never thought they were going to find any! YAY!

https://en.wikipedia.org/wiki/Vulcanoid

:)

Sorry to disappoint there, but these ones aren't *quite* vulcanoids. Although the vulcanoids are supposed to come from the inner solar system, these ones probably came from the vicinity of Jupiter and moved inwards. We are still yet to find any vulcanoids.

Roger E. Moore
2017-Feb-11, 11:49 PM
Picky picky picky, we must throw off our clothes and get drunk! Some of us, that is, not me. Still happy, though.

I mean, it is super cool.