Read More: Science News
Our corner of the galaxy teems with alien worlds. In the 25 years since the discovery of the first planets beyond our solar system, astronomers have found more than 3,600 worlds orbiting other stars. A select few have become tantalizing targets in the search for life despite orbiting stars that are much smaller, cooler — and in many ways harsher — than the sun. Just 39 light-years away, seven planets, all roughly the size of Earth, whirl around a dim red star dubbed TRAPPIST-1, astronomers announced in February (SN: 3/18/17, p. 6). Three are potentially habitable. In April, a team reported the discovery of another world snuggled up to a red sun, LHS 1140b, described by researchers at the European Southern Observatory as perhaps the best candidate in the search for signs of life. And last August, astronomers revealed that not only does a small planet named Proxima b orbit the star closest to the sun, a red neighbor, but it too could support life (SN: 9/17/16, p. 6). All of these worlds orbit faint ruddy stars known as M dwarfs, the most common type of star in the galaxy. Of the roughly 200 planets that have been spied around M dwarfs, dozens are in the coveted habitable zone. It’s this region around a star where a planet could have temperatures that support liquid water, widely considered an essential ingredient for life. But M dwarfs are quite different from the sun, and their planets might be rough places to eke out a living — “the low-rent district of the galaxy,” says Victoria Meadows, an astrophysicist at the University of Washington in Seattle. Harsh flares, bright beginnings and a tight gravitational grip on the innermost planets could be disastrous for any liquid water that’s available. Many more planets are expected to be found in habitable zones around M dwarfs. So researchers want to get a better handle on what these planets are up against. New observations and computer simulations reveal that, while it’s difficult for M dwarf planets to hold on to substantial amounts of water, not all hope is lost. “There are always ways around these things,” says astrophysicist Rory Barnes, also at the University of Washington. M dwarfs and their planet families are plentiful, and there are many conditions in which these worlds can grow and evolve. What’s becoming clear is that any habitable locales around these stars will probably be quite different from Earth.