Experts have been scratching their heads over a huge, bright fireball that zoomed out of the sky over Texas yesterday. Reporters and the FAA claimed it was satellite debris, but astronomers say they're wrong.
Phil Plait of Bad Astronomy has a terrific breakdown of events, explaining how rumors of satellite debris got started and the misinformation was passed around. Confusing matters was the fact that two satellites collided over Earth a couple of weeks ago, so it's possible we might see some junk hitting the planet after such an event. Plus, there was another fireball over Kentucky on Friday. This combination of factors had people believing a rain of satellite parts was falling over the American South.
But after watching the video and doing research on the event, Plait says definitively that it's not space junk:
The video shows the fireball to be moving very rapidly. Typically, meteors come into Earth's atmosphere at 20-50 km/sec (though they can be moving much faster), and burn up 50-100 km high. Man-made space debris re-entering is moving at slower than orbital speed so the max speed is about 8 km/sec. It also burns up lower, and generally you can see flames and whatnot coming off.
I've seen man-made debris re-enter, and it's very different than natural meteors. The difference in speed is very obvious. Right there, that's enough to make me think this was a single natural object.
It's possible to get collisional debris moving more rapidly, but it's difficult. The two satellites closed in on each other at about 10 km/sec, and any shrapnel from that event would most likely be moving at roughly that same speed. If one satellite slammed into, say, an antenna first, then the lower mass antenna might get a pretty hefty acceleration from it, but the amount of energy dumped into it would most likely turn it into a bunch of teeny pieces (remember, the energy of impact was like several tons of TNT). A small object would not have been as bright as the fireball seen.
Also, you'd have to have a pretty special set of circumstances to get any debris from the satellites to re-enter our atmosphere so soon after the collision. It's far more likely that it will be months before we see any of that shrapnel burning up.
So all in all, I am pretty sure what was seen was natural: a rock or a piece of metal from an asteroid.
Read more over at Bad Astronomy!