National Geographic News
New planets discovered.

An artist's impression of two Saturn-like planets orbiting the star Kepler-9.

Image courtesy NASA

Rachel Kaufman

for National Geographic News

Published August 26, 2010

A newly discovered planetary system orbiting a sunlike star may conceal a rare super-Earth, according to data from NASA's Kepler space telescope.

Launched last March, Kepler was designed to look for extrasolar planets, aka exoplanets, via transits—the periodic dimming of light from stars due to planets passing in front them, as seen from the telescope's vantage point. (Read about Kepler's first planet discoveries.)

After analyzing seven months' worth of data from Kepler, a team led by Matt Holman of the Harvard-Smithsonian Center for Astrophysics found two transiting exoplanets orbiting the star Kepler-9, which lies about 2,300 light-years from Earth.

One of the planets, dubbed Kepler-9b, takes just over 19 days to orbit its star. The other, Kepler-9c, takes almost 39 days to complete an orbit. (Find out how exoplanets get their names.)

The researchers noticed that both planets' orbital periods speed up and slow down at regular intervals. This means the two planets are locked in gravitational "resonance"—so that each planet's gravity is affecting the other's orbit.

Using that data, the scientists were able to calculate the masses of the planets, and they found that both worlds are slightly less massive than Saturn.

Newfound Planet System Includes a Hot Earth?

When the astronomers accounted for the amount of stellar dimming the two planets should cause, they found another, faint source of interference.

This signal could mean that a third planet, smaller and nearer to the host star, is transiting Kepler-9 every 1.6 days. The third planet would be about 1.5 times the mass of Earth and made of rocks rather than gas.

(Related: "Newfound Alien Star System Boasts Five, Maybe Seven, Planets.")

But the researchers aren't celebrating just yet—interference from background stars or stellar companions can look a lot like the signals of transiting exoplanets.

"At this point, we have a very, very interesting candidate, and I hope soon we may be able to see something more," Holman said. (Read about the search for new Earths in National Geographic magazine.)

And even if the unknown object turns out to be a super-Earth, humans won't likely be colonizing it: Based on its tight orbit, the planet's surface temperature would be about 2,200 Kelvin (3,500 degrees F, or 1,900 degrees C).

(Related: "'Super Earth' May Really Be New Planet Type: Super-Io.")

The newfound planetary system is described in this week's issue of the journal Science.

1 comments
Chris Matthews
Chris Matthews

Wow. If they find a planet that humans can live on similar to Earth, how long until we start making new technologies and stuff? Then how long until we develop what we need to build something to get us (possibly) light years away to that planet? We should probably be thinking about that right now. Because at this rate, the earth is getting sicker and sicker, because of what we have been doing to it. I don't think this earth has room for everybody's dreams and sastisfaction. We can't build 50,000,000,000,000+ dreams on one earth, without overcrowding it. We aren't doing much good to earth by polluting it either, or poisoning it with what we create to try making it as we want it to be. If anyone has seen the movie "After Earth," moving on to another planet is what we may have to do someday. So some other day, we are going start going nuts developing more space technology at much faster rates, to make creations to colonize us to another Earth-like planet. This is only my imagination. But if this is at all accurate, please write something about this, maybe explaining how this would all really happen. I haven't found any story explaining even theories about how we would colonize, move on to another planet. Please make a story about this, National Geographic.

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