Sunday, August 15, 2010

Another Earth?

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

A newly-discovered planetary system orbiting a sunlike star may conceal a rare super-Earth, according to data from NASA's Kepler space telescope. My thoughts on this are that I am glad that right now it would appear uninhabitable by humans; or else, we would colonize and destroy that poor planet as well.

But I digress. On with the story.

Kepler was designed to look for extrasolar planets, aka exoplanets; and, put into service in March 2009. The way these exoplanets are found is via transits. Transits are the periodic dimming of light emitted from stars when planets pass in front them blocking the light as seen from the vantage point of the Kepler telescope.

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. Kepler-9 is approximately 2,300 light-years from Earth or 135,208,383,583,222,990 miles.

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.

The researchers noticed that both planets' orbital periods speed up and slow down at regular intervals indicating the two planets are locked in gravitational "resonance". Or in other words, 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.

When the astronomers accounted for the amount of stellar dimming the two planets should cause, they found what they consider to be 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.

But the researchers know better than to celebrate just yet. They know that 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.

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).

Via nationalgeographic

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