Scientists find a 'super Earth.' Could it host life?

The team used an extremely sensitive planet-hunting detector, dubbed HARP, bolted to the back of the European Southern Observatory's 3.6-meter telescope at La Silla, Chile. HARP is said to be able to detect an object's velocity to within about two miles an hour of its actual value. Two years ago, HARP nabbed Gliese 581's first planet – similar in mass to Neptune. In the new data the team gathered on the second planet, astronomers also have seen strong evidence for a third planet. Preliminary indications suggest it's orbiting every 84 days and is about eight times more massive than Earth.

Along with Dr. Sasselov, the team is using Canada's "MOST" orbiting telescope starting this week to conduct follow-up studies. MOST is small by just about any standard. Its light-gathering mirror is only about 6 inches across, compared with the Hubble Space Telescope's 94-1/2-inch mirror or the Keck Observatory's twin mirrors, each nearly 400 inches across. Indeed, Canada's plucky instrument has earned a water-cooler name: the Humble Space Telescope.

But what it lacks in size it makes up for in sensitivity to subtle changes in starlight, Sasselov explains. The team will use that sensitivity to monitor Gliese 581 for slight changes in its light as its planets swing across its face.

This "transit" technique for detecting planets can add information that will improve estimates of the planets' masses and other characteristics.

"We expect a very small amount of dimming, maybe one-fifth of 1 percent of the light we receive" from the star, he explains. "That's difficult to do from the ground."

Some researchers have suggested that rocky Earth-like planets orbiting so close to a star, even faint ones like Gliese 581, may not be very hospitable.

Big tides could hurt potential for life

Tidal forces between the star and planet could shut down the planet's rotation. It would present the same face to the star, frying half the planet and freezing the other half. But Sasselov suggests that, at least in this case, tidal forces from the two other planets could moderate the star's effect. Moreover, for even simple life to emerge and adapt, it needs a stable environment over tens of thousands to millions of years, he says. Because super Earths are so massive, their gravity can retain its grip on a thick atmosphere. And theory suggests super Earths would have more-active plate tectonics than Earth itself, he says. This shifting and ripping of the planet's crust renews it with molten material and could represent a stable source of carbon dioxide over geological time scales, potentially allowing for the rise of photosynthesis.

These ideas are speculative for now. Nevertheless, super Earths may "change the whole discussion on what constitutes a habitable planet," Sasselov argues, especially those orbiting red drawfs like Gliese 581.

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