imageGeorge Greenstein,the Sidney Dillon Professor of Astronomy

Interview by Peter Rooney

Scientists recently took the first (blurry) photos of planets orbiting stars other than the sun. George Greenstein (right), the Sidney Dillon Professor of Astronomy, teaches a course titled “The Unseen Universe.” He spoke with Amherst magazine about these no-longer-unseen planets.

Q How significant is this new discovery?
A These are the first photos taken, so it’s very significant. It’s a big deal, and no one thought it was going to be possible for years.

Q More than 300 so-called extrasolar planets have already been found circling distant stars. What makes these discoveries different?
A The 329 planets that we already knew about had been found by using an indirect method to prove a planet exists. No one thought it was going to be possible, without the development of new technology, to actually take a picture and see new planets. Now these people have done it, years before anyone thought it would be possible.

Q What’s known about these planets?
A They’re very much bigger than Earth. And they’re much farther away from the stars they orbit than we are from the sun, so that means they’re much colder.

Q How were these planets found?
A One method used the biggest telescope in the world, the Keck in Hawaii. The Hubble telescope found the other planet. That was a situation in which people knew there was a ring of dust around the star Fomalhaut. People thought that ring of dust is right now in the process of turning into planets—where “now” is in geologic terms, i.e. millions of years. The people using the Hubble found a planet in that ring of dust, and it’s an absolutely newborn planet.

Q How do you pick a planet out of ring of dust so far away?
A It shows up as a tiny dot within the ring. What convinced the astronomers that it really was a planet is that they came back and re-photographed it two years later: they found that it had moved, exactly as a planet orbiting the star would have.

Q What’s next in planetary discovery?
A These planets are not suitable abodes for life. NASA has a series of missions designed to search for planets like Earth. One of them is scheduled to be launched in April. It’s called the Kepler Mission, and it will be able to find much smaller planets than these.

Q What are the odds of discovering an Earthlike planet on another solar system during the next few decades?
A Until this achievement, I would have said that the odds were poor. But these people have shown that new technology and new methods can achieve wonders, so I would say that all bets are off.

Photo by Charles Quigg '09

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