Earthlike Planet

                                                                              Kepler-10c

Scientists announced on Monday that NASA’s Kepler Space Telescope has spied an exoplanet that is 17 times larger than Earth. Kepler-10c has been described as a “Mega-Earth” because it is even too gargantuan to fit into the category of “Super-Earths,” which are about 10 times the size of Earth. Scientists didn’t even think an Earth-like planet this big could exist because it was believed that planets 10 times the mass of Earth would hold on to so much hydrogen gas they would become like Saturn or Jupiter. But Kepler-10c is a rocky, dense planet not enveloped in gas. This discovery suggests there is plenty of room for life to exist on other plus-sized planets.

                                                      NASA’s Kepler Space Telescope

Kepler-10c is also very old, having formed about 11 billion years ago, less than 3 billion years after the birth of the universe. Rocky worlds weren’t believed to have existed that long ago.
“Nature will do what she wants, regardless of earthling theorists,” said Sara Seager, a Massachusetts Institute of Technology planetary scientist 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 thoroughly roasted.
Gravity at the surface is nearly three times that of Earth. If there were creatures somehow bounding around, they would probably be rather squat. The planet is 2.3 times the diameter of Earth but is much denser, particularly toward the core.
“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 University and a co-author of the paper describing the “Mega-Earth.”
The Kepler telescope, launched in 2009, has found the faint signatures of thousands of planets, though some need additional observation before their discovery can be confirmed. The telescope examines a relatively small patch of the sky, taking images of stars and looking for periodic dimming of the starlight. If that dimming follows a regular pattern, it may be from a planet repeatedly passing across the face of the star as seen from the telescope.
Ground-based telescopes have followed up the Kepler leads and gathered new details about these planets. After the space telescope found Kepler-10c, a telescope on the ground measured its mass and discovered that it is a giant, rocky world.
It now appears that planets are extremely abundant — virtually every star may have at least one planet. But the habitability of these worlds remains a mystery. No one has found an exact Earth twin — a rocky, Earth-size world orbiting a sunlike star in the habitable zone.