Tuesday, January 29, 2008

2007 TU24 and the magnetosphere

Today, the asteroid called 2007 TU24 narrowly missed us. By "narrow," I mean about 85 earth radii--1.4 times the distance of the moon. Of course, there are some doomsayers who think this will somehow negatively affect us. They're wrong (duh). Bad Astronomy made an awesome debunking video.

The closest approach has already occurred, but the people at tu24.org don't seem to be letting up. They say they never thought it would hit the earth, and instead think it will cause magnetic disturbance. As it happens, the magnetosphere* is my area of study (mind you, undergraduate research only), and I declare bunk.

They claim that the asteroid traverses the magnetosphere. Well, this is difficult to confirm, since the magnetosphere is constantly changing shape. The magnetosphere extends roughly 15-25 earth radii from the earth, but there is also a very long tail that extends away from the sun. The asteroid just might be in the tail region, but I don't see them actually substantiating such a claim with anything other than this diagram they put together.

In any case, if it did traverse the magnetosphere, this would be of no consequence. Contrary to their claims, the asteroid is electrically neutral, like all large objects. If it had an overall negative charge, then all the surrounding positive ions in interplanetary space would very quickly be attracted to it until it no longer had a charge. So I just don't know how this rock could possibly have a noticeable effect on the magnetosphere. Furthermore, if it did have an effect, we already would have seen it. It doesn't take that long for waves to travel across the magnetosphere--maybe twenty minutes at most.

They throw around ideas like "magnetic reconnection", which is a real phenomenon. But guess what? It's a very common phenomenon that happens all the time even when there is no magnetic activity. Speaking of activity, there was a magnetic storm on November 20. This storm was not, and could not have been caused by a rock. Usually, storms are caused by solar flares and coronal mass ejections. These phenomena are far larger than Earth, and they really do have magnetic properties, since they're made of ionized gas. This gas has no overall electric charge; there are an equal number of positive and negative charges. And yet, do you remember anything happening on November 20? I didn't, and I study this stuff! I only know about it because I checked SpaceWeather.

Really, magnetic storms can have negative effects (see Wikipedia), which is why we need to study it. But mostly they just make pretty lights for the people in auroral regions. And these lights are caused by processes that are far less trivial than 2007 TU24.

*pronounced "mag (as in magnet)-KNEE-toe-sphere"