Scientists have discovered 18 Earth-sized planets beyond the solar system, including one of the smallest known so far and another that could offer conditions friendly to life.
The exoplanets are so small that previous surveys had overlooked them, said researchers at the Max Planck Institute for Solar System Research (MPS) in Germany.The study, published in the journal Astronomy & Astrophysics, re-analysed a part of the data from NASA’s Kepler Space Telescope with a new and more sensitive method that they developed.
The team estimates that the new method has the potential of finding more than 100 additional exoplanets in the Kepler mission’s entire data set. Somewhat more than 4,000 planets orbiting stars outside our solar system are known so far.
Of these so-called exoplanets, about 96 per cent are significantly larger than our Earth, most of them more comparable with the dimensions of the gas giants Neptune or Jupiter.
This percentage likely does not reflect the real conditions in space, however, since small planets are much harder to track down than big ones. Moreover, small worlds are fascinating targets in the search for Earth-like, potentially habitable planets outside the solar system.
The 18 newly discovered worlds fall into the category of Earth-sized planets.
The smallest of them is only 69 per cent of the size of the Earth; the largest is barely more than twice the Earth’s radius. Common search algorithms were not sensitive enough, researchers said.In their search for distant worlds, scientists often use the so-called transit method to look for stars with periodically recurring drops in brightness.
If a star happens to have a planet whose orbital plane is aligned with the line of sight from Earth, the planet occults a small fraction of the stellar light as it passes in front of the star once per orbit. Small planets, however, present scientists with immense challenges.