Earth-like Worlds Come Into View
Newly discovered planets are becoming ever smaller, lighter, and more familiar to us earthlings
An artist's version of a boiling lava sea covering the rocky planet Corot-7b. ESO/L. Calcada |
Actually, “seen” is misleading. What Corot detected was the subtle, repeated dimming of the star Corot-7, 500 light-years away in the constellation Monoceros. This dimming, the team concluded, was caused by a planet orbiting so that it passed directly between the parent star and Earth, a so-called transit. “They’ve gone to great lengths to rule out any other explanations,” says David Charbonneau of the Harvard-Smithsonian Center for Astrophysics, a friendly rival of the Corot scientists.
The amount of dimming—less than one-thirtieth of a percent —tells the astronomers that their new world, provisionally named Corot-7b, is about 15,000 miles wide. Its “year” is just 20.4 hours long because it orbits so close to its star, with daytime temperatures nearing 2,000 degrees Fahrenheit. By September, Didier Queloz of the Geneva Observatory had weighed Corot-7b. Using the High Accuracy Radial Velocity Planet Searcher, or HARPS, at the European Southern Observatory in Chile, his team measured the planet’s gravitational influence on its parent star. The verdict: The planet is five times the mass of Earth and has about the same density, suggesting it is made of rock. In raw form, the new planet resembles our own world.
And the real jackpot may not be far off. In March NASA’s Kepler satellite went into an unusual, Earth-trailing orbit looking for transiting planets. Its telescope is bigger than Corot’s, its orbit is more stable, and it is slated to scan 100,000 stars, while Corot is limited to 12,000. “If other Earths are out there,” says Kepler team member Charbonneau, “we’re going to find them.”
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