Prof Maps Extrasolar Orbit

A group of researchers, including Columbia astronomy professor Kristen Menou, has used a NASA telescope to create a detailed map of a planet's orbit outside of our solar system for the first time.

The groundbreaking research, which was announced Thursday and published this week in Science magazine, could provide scientists with valuable information about the nature of planets outside of our solar system and the process by which planets are formed. While previous observations relied on visible light, this one used NASA's Spitzer Space Telescope to track the orbit of the planet with infrared light, which can only be observed from outside Earth's atmosphere.

"Infrared light is not reflected light," said Menou. "What defines day and night on Venus is reflected light from the sun. What we see in infrared is light absorbed by the planet and re-emitted."

The planet is a large, close-orbiting gas planet from a class known as hot Jupiters. As it orbited its mother star-located 40 light-years away in the Andromeda constellation-the scientists observed a smooth and consistent fluctuation of infrared light from the solar system. This suggests that the planet is not consistently emitting infrared light but rather has a hot side and a cold side.

Unlike planets within our solar system, the hot Jupiter rotates on its axis at the exact same rate as it is orbiting its mother star.

"It's a little bit of a surprise," Menou said. "The planet is showing the same face at all times to the star, so it has a permanent dark side."

While the ramifications of the research are unclear, one expert said that the results could give scientists a glimpse of atmospheric conditions on the planet or even information on what the planet's surface looks like.

"It's quite a major step towards understanding the actual physical characteristics of other worlds around other stars," said Caleb Scharf, director of astrobiology at the Columbia Astrobiology Center. "It's going to enable us to not only understand details about how they're being heated by their parent star, but also how they respond to that."

For example, Menou said that planets in our solar system are very efficient at distributing heat with winds, in which case there would not be such a large disparity in energy on the light and dark sides of the planet. That's not the case on this planet, and that could allow scientists to predict its appearance.

Scharf said that the research could also clarify the still mysterious process of planet formation.

"We think there's a common mechanism, that everywhere you make planets by one set of rules, but we don't know what those rules are," he said. "Even though they're nothing like the planets in our solar system, it leads us to a central understanding about the planets in our solar system."

Scharf added that Menou's involvement could bring money and attention to Columbia.

"This is really, really cutting-edge stuff, so to have someone here working on this is terrific. It stimulates students, and we hope it will contribute to interest in what we're working on here," Scharf said. "It opens up an avenue to federal funding. We also like to think that exciting stuff like this opens up avenues to people who want to contribute to the University as well."