A NASA telescope taking a nose count of planets in one small neighborhood of the Milky Way registered more than 1,200 candidates, including dozens of planets residing in life-friendly orbits around their parent stars. Scientists have no way of knowing yet if any of the newly discovered planets are solid-body worlds like Earth. But the census, collected by NASA's Kepler Space Telescope after just four months of work, shows that small planets like Earth are much more prevalent than Jupiter-sized worlds and that multiple-planet systems are common.
"We think we're seeing about 200 multi-planet systems," astronomer Daniel Fabrycky, with the University of California, Santa Cruz, told Discovery News. "That really blew us away. We didn't expect that this would be one of Kepler's discoveries."
The Kepler telescope sees a planet's footprints as it passes across the face of its parent star, just like a gnat flying past your computer screen will block a bit of light.
When a planet orbits behind the star, relative to Kepler's view, there is a slight increase in brightness. From the frequency and duration of the dimming and brightening scientists can figure out how far away a planet orbits and how much mass it contains.
Kepler, which monitors stars in the constellation Cygnus, was launched to find out how many Earth-like worlds are orbiting a sampling of 156,000 stars like the sun.
Actually finding an Earth-sized world circling as far from its star as Earth orbits the sun will take 365 days of observations to detect one pass, plus another year or two of data to verify the orbital period.
If Kepler's latest head count is confirmed, the list of extrasolar planets will more than triple.
"One of the things that is still a work in progress is to figure out how many of the candidate planets are real planets," Jonathan Fortney, assistant professor of astronomy and astrophysics at University of California, Santa Cruz, told Discovery News.
An independent analysis by astrophysicists at the California Institute of Technology (Caltech) shows Kepler's track record of finding extrasolar planets is better than 80 percent.
The CalTech analysis appears on arXiv.org. The Kepler science mission data, collected between May 2 and September 16, 2009, will be published in an upcoming issue of The Astrophysical Journal.
