Earth’s bigger, older cousins
Astronomers have discovered the largest rocky planet yet, and its existence has profound implications for our understanding of the early universe and the potential for extraterrestrial life. Kepler-10c, which was spotted by NASA’s Kepler space telescope, has a diameter of roughly 18,000 miles—more than twice that of Earth —prompting scientists to create a new class of planets, dubbed “mega-Earths.”The body’s rocky composition was a surprise, as any planet that large was expected to attract hydrogen as it formed, resulting in a Jupiter-like gas giant.
What’s more, Kepler-10c orbits a star about 560 light-years away in a solar system that is 11 billion years old, indicating that the planet may have formed less than 3 billion years after the Big Bang, when the universe contained mostly hydrogen and helium. The heavier elements, like silicon and iron, were produced in star explosions, and astronomers had theorized that several generations of stars had to come and go before those elements would occur in sufficient quantities to form large, solid planets. But “finding Kepler-10c tells us that rocky planets could form much earlier than we thought,” Dimitar Sasselov, director of the Origins of Life Initiative at Harvard University says. “And if you can make rocks, you can make life.”