16 Jupiter-sized planets identified


October 06, 2006|By Frank D. Roylance

Using the Hubble Space Telescope to peer straight into the hub of the Milky Way galaxy, astronomers at the Space Telescope Science Institute in Baltimore have found evidence of 16 more Jupiter-sized planets, each circling its own sun.

These new planet candidates are the most distant - some 26,000 light years from Earth - of the more than 200 "extrasolar" planets detected so far. Their abundance, the astronomers say, suggests our galaxy alone may hold 6 billion planets at least as big as Jupiter.

The discovery team was led by the institute's Kailash Sahu. Their work, reported yesterday in the journal Nature, was part of Hubble's Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) project.

Over seven days in February 2004, Hubble monitored 180,000 stars near the center of the Milky Way's spiral, watching for periodic dimming that would signal the passage of an unseen planet in front of its star.

Five of the 16 planets they detected are whipping around their stars so fast that they constitute a new class of ultra-short-period planets. On one of them, a "year" lasts just 10 hours. It orbits only 750,000 miles above its star - three times the Earth-moon distance.

That was "a big surprise," Sahu said. "Our discovery also gives very strong evidence that planets are as abundant in other parts of the galaxy as they are in our solar neighborhood."

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