Exoplanets seem to be a dime a dozen these days — and even ones with two (or even three) suns in their sky have lost a bit of their wow factor. But the latest discovery of a "Tatooine" manages to stand apart. For the first time, scientists have spotted one of these circumbinary systems with help from a phenomenon called gravitational microlensing: The planet is so massive that it warps space-time around it, bending light in a way that magnifies the planet into our line of sight.
The OGLE-2007-BLG-349 star system (named for the Optical Gravitational Lensing Experiment, or OGLE) is 8,000 light-years away. But in 2007, the stars aligned: A planet now dubbed OGLE-2007-BLG-349Lc (let's call it 349Lc for short) passed in front of its host stars from the perspective of our telescopes. When this happens in certain systems, we can catch what we call "transiting" events — the dim of a star as the planet passes in front of it — or slight wobbles in the star's light as it plays tug-of-war with its planet's gravity.
But in this case, scientists saw a "microlensing" event. When 349Lc moved in front of its stars, its massive gravity warped their light like a giant magnifying glass suspended in space. By analyzing the resulting data (including follow-up observations with the Hubble telescope) researchers determined that the objects being warped by 349Lc were indeed stars, plural, in the right place to be a pair of suns.
These results, soon to be published in Astronomical Journal, represent the first time a multistar system has been confirmed using this cosmic optical illusion. That has some exciting implications for future exoplanet discovery, because 349Lc — which orbits 300 million miles away from its tightknit pair of red dwarf suns — is too far from its stars for scientists to have detected any of the dims or wobbles used in most exoplanet discovery.
“This discovery suggests we need to rethink our observing strategy when it comes to stellar binary lensing events,” Yiannis Tsapras, a co-author of the study from the Astronomisches Rechen Institut in Heidelberg, Germany, said in a statement. “This is an exciting new discovery for microlensing.”