Neighborhood Watch
At first glance, an asteroid might seem like a hard thing to lose. Many asteroids are as big as football fields, mountains, or even cities. And yet astronomers sometimes lose track of these chunks of cosmic rock and metal. For the asteroids that cross or come close to Earth's orbit, that could be dangerous: These objects could someday slam into our planet, so it's crucial for us to know where they are.
Astronomers at McDonald Observatory are helping make sure we know just that. Judit Ries and her colleagues follow up the discoveries of near-Earth asteroids to help plot their orbits more accurately. They also track down asteroids that haven't been seen in a while to make sure we know where they are.
Astronomers don't actually "lose" asteroids. It's just that it sometimes takes a while to find them.
When an asteroid is discovered, astronomers plot its orbit based on just a few observations. But these early plots can have large margins of error. As a result, an asteroid that no one's looked at in several years might not appear where astronomers expect it to.
So it's important to see an asteroid and record its location many times over a period of several years. These observations help astronomers plot a much more precise orbit, so they know where to find the asteroid many years in advance. That allows them to identify the asteroids that might someday hit Earth -- long before they're a serious threat.
Script by Damond Benningfield, Copyright 2005
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