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| Kepler Space Telescope spies a ‘Mega-Earth’ | Kepler Space Telescope spies a ‘Mega-Earth’ |
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| You can add to the growing list of “exoplanets” a huge, dense, surprisingly rocky world with 17 times the mass of Earth. Discovered by NASA’s Kepler Space Telescope and announced Monday at an astronomy meeting in Boston, this new planet, officially named Kepler-10c, scrambles the equations that dictate how massive a rocky planet can be without ballooning into a Jupiter-like gas giant | |
| There have been Earth-sized rocky planets found out there in deep space, and a surprising number of “Super-Earths” that are up to 10 times the size of our own planet, but this one seems to fit into a category all by itself: a “Mega-Earth.” | There have been Earth-sized rocky planets found out there in deep space, and a surprising number of “Super-Earths” that are up to 10 times the size of our own planet, but this one seems to fit into a category all by itself: a “Mega-Earth.” |
| The theorists didn’t see this coming. The orthodoxy was that, beyond about 10 Earth masses, a planet would hold onto so much hydrogen gas that it would become like Jupiter or Saturn. The fact that plus-size planets can stay rocky, with clearly defined surfaces rather than a dense envelope of gas, should indicate that there’s plenty of real estate out there where life as we know it could thrive. | The theorists didn’t see this coming. The orthodoxy was that, beyond about 10 Earth masses, a planet would hold onto so much hydrogen gas that it would become like Jupiter or Saturn. The fact that plus-size planets can stay rocky, with clearly defined surfaces rather than a dense envelope of gas, should indicate that there’s plenty of real estate out there where life as we know it could thrive. |
| “Nature will do what she wants, regardless of Earthling theorists,” said M.I.T. planetary scientist Sara Seager, who was not involved in the new discovery but said by e-mail that she finds it “incredibly exciting.” | “Nature will do what she wants, regardless of Earthling theorists,” said M.I.T. planetary scientist Sara Seager, who was not involved in the new discovery but said by e-mail that she finds it “incredibly exciting.” |
| Kepler-10c, which orbits a star 560 light-years away in the constellation Draco, isn’t likely to harbor life — it is too close to the parent star and the surface is roasted. If there were creatures somehow bounding around they’d likely be very squat. Gravity at the surface is about twice that of Earth’s gravity. The planet is 2.3 times the diameter of Earth, but is much denser. | Kepler-10c, which orbits a star 560 light-years away in the constellation Draco, isn’t likely to harbor life — it is too close to the parent star and the surface is roasted. If there were creatures somehow bounding around they’d likely be very squat. Gravity at the surface is about twice that of Earth’s gravity. The planet is 2.3 times the diameter of Earth, but is much denser. |
| “It’s still rock, but it’s rock that’s twice as dense as the rock we’re used to,” said Dimitar Sasselov, a professor of astronomy at Harvard. | “It’s still rock, but it’s rock that’s twice as dense as the rock we’re used to,” said Dimitar Sasselov, a professor of astronomy at Harvard. |
| The Kepler Space Telescope has found hundreds of planets and thousands of possible planets as it scrutinizes a relatively small patch of the sky. The telescope looks for periodic dimming of starlight as a planet transits the face of the star. It has long been assumed that planets are common in the universe, but now there is solid data, and it may be that virtually every star has at least one planet. | The Kepler Space Telescope has found hundreds of planets and thousands of possible planets as it scrutinizes a relatively small patch of the sky. The telescope looks for periodic dimming of starlight as a planet transits the face of the star. It has long been assumed that planets are common in the universe, but now there is solid data, and it may be that virtually every star has at least one planet. |
| Less clear is the question of habitability. One bulletin Monday from the American Astronomical Society meeting in Boston offered a reminder that there are a lot of ways that a planet can prove to be inhospitable to life. The “space weather,” for example, might be ghastly. | Less clear is the question of habitability. One bulletin Monday from the American Astronomical Society meeting in Boston offered a reminder that there are a lot of ways that a planet can prove to be inhospitable to life. The “space weather,” for example, might be ghastly. |
| Astrophysicist Ofer Cohen of the Harvard-Smithsonian Center for Astrophysics modeled the environments of three possible planets identified by the Kepler telescope, each apparently rocky like the Earth and orbiting their parent star in what is deemed the “habitable zone,” the region where water could potentially be liquid at the surface. | Astrophysicist Ofer Cohen of the Harvard-Smithsonian Center for Astrophysics modeled the environments of three possible planets identified by the Kepler telescope, each apparently rocky like the Earth and orbiting their parent star in what is deemed the “habitable zone,” the region where water could potentially be liquid at the surface. |
| All three of those parent stars are common “red dwarfs,” also known as “M-dwarfs,” which account for about seven of every 10 stars in our galaxy. The “habitable zone” of these small stars is relatively close. But that brings into the equation another factor: The stellar wind, the particles streaming from the star’s surface. Cohen concluded that the stellar wind would likely have stripped away the atmospheres of these planets. | All three of those parent stars are common “red dwarfs,” also known as “M-dwarfs,” which account for about seven of every 10 stars in our galaxy. The “habitable zone” of these small stars is relatively close. But that brings into the equation another factor: The stellar wind, the particles streaming from the star’s surface. Cohen concluded that the stellar wind would likely have stripped away the atmospheres of these planets. |
| “These planets don’t reside in a vacuum, they reside in a medium that has a continuous flow of particles, mostly protons, that are emitted by the star,” Cohen said. | “These planets don’t reside in a vacuum, they reside in a medium that has a continuous flow of particles, mostly protons, that are emitted by the star,” Cohen said. |
| This is what happened to Mars, he said. Long ago it had a protective magnetic field, as does the Earth, and it held onto its atmosphere in the face of the solar wind. But Mars then lost its magnetic field, and solar wind stripped away the Martian atmosphere, he said. | This is what happened to Mars, he said. Long ago it had a protective magnetic field, as does the Earth, and it held onto its atmosphere in the face of the solar wind. But Mars then lost its magnetic field, and solar wind stripped away the Martian atmosphere, he said. |
| This new research might alter the strategy of astronomers looking for truly Earth-like planets in habitable zones. | This new research might alter the strategy of astronomers looking for truly Earth-like planets in habitable zones. |
| “Maybe we should not focus on M-dwarfs, even though those are so common. Maybe we should focus on the more sun-like stars,” Cohen said. | “Maybe we should not focus on M-dwarfs, even though those are so common. Maybe we should focus on the more sun-like stars,” Cohen said. |
| Related: | Related: |
| 1,676 planets beyond solar system | 1,676 planets beyond solar system |
| Series: The future of NASA and space exploration | Series: The future of NASA and space exploration |
| Kepler telescope doubles number of known planets outside solar system | Kepler telescope doubles number of known planets outside solar system |