Thursday, December 16, 2010

Is Asteroid Scheila Really Comet Scheila?

I started the month with a couple of news stories and a post about how I didn’t want to let interesting news stories “get old” just because I didn’t have anything in particular to say about them. Today is an example of that.

This is a picture and news story about an asteroid that astronomers have discovered acting like a comet:

When is an asteroid not an asteroid? When it turns out to be a comet, of course. Has this ever happened before? Why, yes it has. In fact it was just announced December 12, 2010 that the asteroid (596) Scheila has sprouted a tail and coma! This is likely a comet that has been masquerading as an asteroid.

Steve Larson of the Lunar and Planetary Laboratory (LPL), University of Arizona first reported that images of the minor planet (596) Scheila taken on December 11th showed the object to be in outburst, with a comet-like appearance and an increase in brightness from magnitude 14.5 to 13.4. The cometary appearance of the object was confirmed by several other observers within hours.

A quick check of archived Catalina images of Scheila from October 18, November 2 and November 11 showed Scheila to look star-like, which is what asteroids look like from Earth. They just happen to be moving across the field of view in contrast to the fixed background stars. The image taken by Catalina on December 3rd shows some slight diffuseness and an increase in overall brightness. So, it appears this event began on or around December 3rd.


This is really interesting stuff and I’ve briefly mentioned volatile material in the asteroid belt once or twice before.

Pluto And Beyond #3: The Golden Age of Outer Solar System Studies

Solar System Formation And Really Odd Explanations

It’s remarkable because so far as anybody knows, there is no mechanism for new material to enter the asteroid belt. It is believed to be made up of material from the very birth of the solar system. If the solar system is in fact billions of years old, then how can there still be volatile material in the asteroid belt? Even if the material only flares intermittently, over the course of billions of years models suggest there should be no volatile materials left in the asteroid belt.

This has been an issue for a number of years because it has—of all things!—religious implications.

So-called Young Earth Creationists believe that the solar system is only thousands of years old. Therefore it is not—to their way of thinking—unusual or unexpected to have volatile material in the asteroid belt or anywhere else.

Almost all astronomers and astrophysicists reject that thinking as ridiculous and accept “deep time,” a solar system that’s billions of years old, as an established fact or even as an axiomatic truth.

But comets have always posed a problem to the accepted viewpoint. First the high number of existing comets led astronomers to predict a thing called the Kuiper belt, a vast collection of comets at the outer fringe of the solar system. When that didn’t seem to create an appropriate reserve of comets, astronomers predicted a thing called the Oort cloud, an even more vast collection of comets in something like a sphere around our solar system.

Scientists kind of try to have their cake and eat it too in this instance. On one hand these new and newer mechanisms for generating comets are seen as science being self-correcting and explaining new data using elaborations of well-understood models. On the other hand—mostly in private—scientists are a little uneasy depending on what are basically kludges, possibly a modern example of epicycles, to explain a common phenomenon like comets.

Because amateurs have such great telescopes these days, and because so much professional data goes almost directly to the web, this intriguing situation is playing out in public—although the mainstream media almost never discuss the religious issues—and it is going to be interesting to see what new surprises the asteroid belt and comets provide and how scientists and creationists deal with the data.

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