Kepler epitaph? Eight most intriguing finds of troubled telescope.

Kepler, the space telescope designed to help us find other Earth-like planets, is on the fritz. Scientists hope they will be able to fix it remotely, but if they can't, its brief, brilliant career could be over. Here are eight of its most important discoveries.

3. Kepler-11: Bizarre solar system

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    This artist's conception shows Kepler-11, a sun-like star around which six planets orbit.
    Tim Pyle /NASA/File
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Often, the most exciting scientific discoveries are those that aren't explainable by current scientific theories. The Kepler-11 system certainly left researchers scratching their heads.

The orbits of the first five planets could fit inside Mercury's orbit. The sixth could fit inside Venus's orbit. Finding so many planets bunched so close together was surprising enough. What made the discovery even more perplexing is that these weren't Mercury-size planetary minnows. Each was 2 to 4 times larger than Earth. 

And they weren't the same. The two innermost planets appeared to be a mix of rock and water, while the low mass of the next three suggest that "a substantial fraction of their volume must be made of hydrogen and helium gases," Jack Lissauer, a member of the Kepler team, told the Monitor when the announcement was made in February 2011.

It's a planetary system "of a type we had no idea existed," he said.

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