Potentially dangerous asteroids
NASA astronomers tracked down about 100 small asteroids by hunting through more than 28,000 archival images taken by the Hubble Space Telescope. Here is a sample of what they have found. (Photo: NASA)
Dr. Lance Benner of NASA’s Deep Space Network tracks asteroids that sweep close to Earth. Earth & Sky’s Jorge Salazar spoke to Benner.
Salazar: What is a “potentially hazardous asteroid?”
Benner: If an object is classified as potentially hazardous, it doesn’t mean that you should head for the hills or buy a hard hat or run for your life or anything. That’s not the point.
The point is to identify objects that merit particular attention by astronomers, merit particular efforts to track them over long periods of time to find out where their orbits are.
Potentially hazardous asteroids are, by definition, objects that can approach Earth within a certain minimum distance and are larger than a certain size. The size is about 200 meters, and the minimum distance that they can approach is about 5/100 of the distance between the Earth and the sun.
To give you a sense of perspective, there are currently 4,070 asteroids known that can approach within 30 percent of the distance between the Earth and the sun. Out of those 4,070, 784 of them are officially classified as potentially hazardous.
Of all of those objects, the one that has the highest probability of hitting us has a very low probability, and it’s 900 years from now.
So you don’t need to worry now, but we definitely need to pay attention.
We want to keep looking at these objects just in case one comes along that has our name on it.
Salazar; Why is it important to study the objects – even the ones that are in no danger of hitting us?
Benner: Scientifically, there are a number of reasons why we’re interested in these objects. For one thing, it’s thought that near-Earth asteroids are the source of meteorites.
Meteorites are small rocky objects, in some cases metallic, that penetrate the Earth’s atmosphere and strike the ground. They’re very important because they’ve told us most of what we know about the very early history of the solar system.
In addition, we’re trying to understand what these asteroids can tell us about the current number of these objects, how big they are, how fast they rotate. These are all things that we need to know if we find one that is actually on a collision course with Earth. We need to know what its made of, we need to know how big it is, how fast it is, if it’s one object or two.
We’ve found that 15 percent or 16 percent of these objects that are bigger than 200 meters in diameter are actually double objects. They’re like a miniature version of the Earth and the moon.
