News & Events Who Knows: Astronomy Professor George Greenstein and the first photographic evidence of “Extrasolar Planets”

It was a discovery some thought might not occur for decades:  the first photos – blurry yes, but photos nonetheless – of planets orbiting stars other than the sun. Not surprisingly, the discovery has excited the astronomy community around the world. George Greenstein, the Sidney Dillon Professor of Astronomy at Amherst, happens to be teaching a course this semester titled The Unseen Universe. He spoke with Public Affairs Director Peter Rooney recently to offer insight on these no longer unseen planets.

PR: The first photos were taken recently of what astronomers say are planets going around other stars in another solar system.  How significant is this?

GG: 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.

PR: More than 300 so-called extra solar planets have already been found circling distant stars. What makes these discoveries different?

GG: The 329 planets that we already knew about had been found by using an indirect method that prove a planet exists. No one thought it was going to possible without the development of new technology to actually take a picture and see new planets.  Now these people have done it and done it years before anyone thought it would be possible.

PR: What’s known about these planets?

GG: What’s known is they’re unlike Earth; 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.

PR: How were these planets found?

GG: They used two different methods. One method used the biggest telescope in the world, the Keck in Hawaii. It has this marvelous technology in which the mirror, which is what magnifies the image, is constantly flexing its shape to compensate for the twinkling of the stars. It detects the twinkling of the stars and changes its shape to cancel out the twinkling. It’s really marvelous technology.

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 new-born planet.

PR: How do you pick a planet out of a ring of dust so far away?

GG: 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.

PR: What’s next in planetary discovery?

GG: Now that people have developed these techniques, they’re going to keep discovering planets. The big issue is that these planets are much bigger than Earth, and much colder, so that they are not suitable abodes for life. So, 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.

PR: What are the odds of discovering an Earthlike planet on another solar system during the next few decades?

GG: 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.