Where in the Solar System is the Asteroid Belt?
I’ve been thinking about asteroids this week. Did you know that on October 12, 2010 an asteroid called 2010 TD54 passed within 28,000 miles of the Earth? That’s pretty close. In fact, it passed within the orbit of the moon and close to the orbit of some of our own satellites. That got me thinking about where asteroids are located and just how many of them are out there. I’m also wondering about what the chances are of one of those things actually hitting the Earth!
Asteroids are small rocky and metallic bodies that are not planets or comets. They vary greatly in size from almost 1,000 kilometers (small planet size) to rocks just meters across. They are generally irregularly shaped and are thought to be the remnants of early planetary formation. It is estimated that there are well over 30,000,000 of these objects in our solar system. The largest asteriod, which is actually called a planetoid, is Ceres. Ceres has a diameter of 975 km or 610 miles.
The majority of asteroids can be found in the asteroid belt . The asteroid belt is located between the orbits of the planets Mars and Jupiter. This location is also known as the main asteroid belt. Other types of asteroids are near earth asteroids (can you guess where they are located?) and trojan asteroids.
It is estimated that tiny asteroids – those with diameters between 5 – 10 m (16 to 33 ft) enter the Earth’s atmosphere about once a year. This is not a big problem because they are obliterated in the upper atmosphere. Only the big ones can get through – those that have a diameter of over 50 meters (164 ft). The last time one that big hit the Earth was most likely the Tunguska event in 1908.
As you might imagine, NASA keeps track of all these small objects. The Near Earth Object Program website has orbit diagrams and lists close approaches.
By the way…2010 TD54 was pretty small. NASA estimated that it was roughly 15-30 feet in diameter and if it did hit the atmosphere, it would have quickly burned up. Whew!