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.

2. Kepler-10b: Molten world

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    This artist's rendering of Kepler-10b shows a scorched world orbiting at a distance that’s more than 20 times closer to its star than Mercury is to our own sun.
    Dana Berry/Kepler Mission/NASA/File
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Before Kepler found its first Goldilocks planet-candidate in Kepler-22b, it achieved another planet-finding first. Kepler-10b was the first-ever confirmed Earth-size rocky planet outside our solar system.

It radius is only 1.4 times the size of Earth's, and the discovery of such a small planet-candidate was heralded as historic when it was announced in January 2011.

But the comparisons with Earth virtually end there. The planet is so close to its star – 20 times closer than Mercury is to the sun – that its orbit lasts only 20 hours and 10 minutes. Its sun-facing side is estimated to be 2,500 F, so hot that parts of its surface could be molten. Sun-seared flecks of the planet could trail behind it, comet-like.

Moreover, despite the fact that it is about the same size as Earth, Kepler-10b is 4.5 times more massive and denser than iron, giving it a gravitational field twice as strong as Earth's. Some scientists posit Kepler-10b could be the core of a gas-giant planet whose atmosphere has boiled away as it moved nearer its star.

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