Worlds beyond the Milky Way
Scientists have discovered the first evidence of planets in a galaxy far, far away. NASA had previously confirmed the existence of more than 3,500 planets that orbit stars other than the sun. But those exoplanets are all within our galaxy, the Milky Way, which spans roughly 100,000 light-years. Now astrophysicists have detected exoplanets in another galaxy 3.8 billion light-years away, using data from NASA’s Chandra X-ray Observatory space telescope. Those planets are so distant that they can’t be directly observed, “not even with the best telescope one can imagine in a science fiction scenario,” study co-author Eduardo Guerras tells Smithsonian.com. Instead, the scientists looked at light coming from a quasar—a supermassive black hole surrounded by a disc of gas—some 6 billion light-years away, and examined how it was being bent by the gravitational force of the distant galaxy. That technique, called gravitational microlensing, has revealed that the galaxy is likely home to more than a trillion planets—objects ranging from moon- to Jupiter-size. “This is very cool science,” says Guerras.
Ranja Andriantsoa/DKFZ, Univ. of Oklahoma, Newscom ■