The Verge: It’s a huge discovery — since even Albert Einstein didn’t think such a thing would be possible to observe. Now that we’ve proved Einstein wrong (but also right), astronomers hope to spot even more events just like this, as well as use these occurrences to learn more about the stars in our Universe. by Loren Grush
'Einstein first predicted gravitational microlensing in his theory of general relativity. It works kind of like how it sounds: it’s gravity acting like a lens that can manipulate light. Basically, supermassive objects — such as stars and black holes — warp space and time around them. This warped space-time can then act like a magnifying glass, changing the path that light takes through the Universe. Specifically, microlensing can occur when one star — the “source” — passes directly behind another star — the “lens” — along our line of sight from Earth. The gravity from the lens warps the light from the source, making it appear brighter and slightly distorted.
'These events require stars that are very far apart to line up perfectly. That’s why Einstein once wrote that "there is no hope of observing this phenomenon directly." Our telescope technology has become far more sophisticated than in Einstein’s day — which is what allowed us to observe something he thought we’d never see. In 2014, a group of astronomers using NASA’s Hubble Space Telescope spotted a rare type of microlensing, when a dense white dwarf star passed in front of another star thousands of light-years away. The stars weren’t exactly aligned, but they were close enough that the white dwarf made it seem like the background star performed a small loop in the sky. “It looks like the white dwarf pushed it out of the way,” Terry Oswalt, an astronomer at Embry-Riddle Aeronautical University who was not involved in this discovery but wrote a perspective piece in Science, tells The Verge. “That’s not what happened, of course. It just looks like that.”'