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Deep Impact
BNH talks to David Rabinowitz, research associate in the Yale Department of Physics, about his current research on near-Earth asteroids.
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Business New Haven
2/7/2000
By: Tammy Rachau
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What would be the effect of an asteroid hitting the Earth?
It is not really certain what the effects would be, because the effects that we've seen in the past are only in the geologic record. For the largest impacts, there is a consensus now among scientists that there was a mass extinction 65 million years ago. This mass extinction was caused by a very large asteroid, about ten kilometers. We expect that maybe not quite as devastating an effect would take place, but still a global catastrophe would occur if something a kilometer or larger were to hit the Earth.
Give us a brief overview of your current research on near-Earth asteroids.
I was hired to come to Yale University to work with the physics department on an astronomy project. I worked at the Jet Propulsion Laboratory (JPL) with Eleanor Helin, an astronomer there interested in surveying for near-Earth asteroids - taking a telescope and using it each month to cover as much sky as possible and look for asteroids that have orbits that take them near the Earth. These are asteroids that in the far distant future or some time in the future could hit the Earth. That was my previous job. The paper that we published together in Nature describes our estimate for the total number of asteroids on this kind of orbit that are larger than one kilometer. Our new estimate of the number is about 700, plus or minus 230 asteroids. In other words, about 500 to 1,000. .
What technique do you use to survey the asteroids?
We use a telescope that by professional standards is a modest one, about 36 inches in diameter, that belongs to the Air Force. We mount at the focus of the telescope a very sensitive electronic detector that we built at the Jet Propulsion Lab. That allows us to see asteroids that are very faint, so that we can find the asteroids when they are far from the Earth. We then use a computer to read out the digital image. The computer inspects it for images of asteroids, and it can tell that something is an asteroid because of the way it moves relative to the background stars.
Is this part of a collective scientific effort to survey these asteroids?
Yes, it is a collective effort we are a part of to survey as close as we can to the entire population of near-Earth asteroids - one, in order to know how many there are, and two, to make sure there aren't any on their way toward Earth. We think that there is a very, very small likelihood that one would hit in the next hundred years. There would be a one in 1,000, or even less, chance. But still, if one did hit, the effect would be so devastating that it really is worth the effort to do find them ahead of time. Right now what is under way is a ten-year effort to survey the entire population. It is a worldwide effort, although most of it is being done by groups in the U.S.
Is your work on developing the largest electronic camera related to the survey of the near-Earth asteroids?
It is going to be used for the surveying, but it is going to be used for other research as well. My primary role here at Yale is to help develop a camera for the physics department; it is actually an astrophysics project. The head of the department, Professor Charles Baltay, is conducting an experiment in using a telescope to search for the most distant galaxies that you can see from the Earth. These are called quasars. They emit a lot of energy, but they are very distant.
If we did find out that an asteroid was headed toward Earth, could we do anything about it?
Yes, we probably could, depending on when it comes. If we would know about it hundreds of years ahead of time, and we believe that we will if we conduct the survey in a short enough time, then we would have plenty of time to develop a strategy. We could study the asteroid, we could send a space probe there to determine its composition and structure. Then we could determine if we needed some kind of engine to divert it, a bomb of some kind to divert it, or even something as gentle as a solar sail - a canopy that would use sunlight to redirect the path. If you have a long time, there are a variety of techniques that would work to divert an asteroid. But it is something that we would have hundreds of years to develop.
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