Thursday, January 3, 2008

A Second Earth in the Making


A new solar system containing an Earth-like planet is likely to be forming 424 light-years away around a 10 million-year-old star named HD 113766, a team of astronomers using NASA’s orbiting Spitzer Space Telescope have discovered.

At this point, the new solar system isn’t much to look at — it’s just a huge belt of warm dust, swirling around a star that is slightly bigger than the sun. But the dust is located smack in the middle of HD 113766’s habitable zone — that is, the region around a star in which the surface temperature on a planet would allow water to exist in liquid form. (The Earth, for example, is located precisely in the middle of the sun’s habitable zone, which sometimes also is called the ecosphere.) HD 113766 also happens to be just the right age for forming rocky planets like those in our inner solar system.

"The timing for this system to be building an Earth is very good," Casey Lisse, a senior research scientist in the space department of the Johns Hopkins University Applied Physics Laboratory in Baltimore, explained in a press release. “If the system was too young, its planet-forming disk would be full of gas, and it would be making gas-giant planets like Jupiter instead. If the system was too old, then dust aggregation or clumping would have already occurred and all the system's rocky planets would have already formed."

According to Lisse, the conditions for forming an Earth-like planet are more than just being in the right place at the right time and around the right star — it's also about the right mix of dusty materials. Using Spitzer’s infrared spectrometer, he determined that the material in the dust belt is more processed than the snowball-like ingredients of infant solar systems, but not as far along as mature planets. That means that the dust belt is in a transitional phase, where planets are just beginning to form.

"The material mix in this belt is most reminiscent of the stuff found in lava flows on Earth. I thought of Mauna Kea material when I first saw the dust composition in this system — it contains raw rock and is abundant in iron sulfides, which are similar to fool's gold," says Lisse.

Here’s a 2004 scientific journal article about the formation of solar systems around young stars. Here also is an artist's conception of the forming solar system.