Hubble Telescope Spots a Distant Planet Orbiting Twin Suns
NASA scientists have discovered a gas giant as massive as Saturn in an orbit around two red dwarfs. The distance between the two stars is 110 lakh kilometers, or thirty times the distance between the Earth and the Moon. The planet orbits at a distance of 482 crore kilometers from the two stars, which is roughly the distance between our Sun and the Asteroid Belt. The planet takes seven Earth years to orbit around the stars.
This is the first time that a three body system was discovered using the gravitational microlensing technique. When viewing two aligned stars from the Earth, the foreground star bends and amplifies the light of the background star, a phenomenon known as gravitational microlensing. The specific properties of the light can be used to identify characteristics of the foreground star and associated planets.
The starfield was crowded because the system is 8000 light years towards the center of the Milky Way Galaxy, which is dense in stars. The sharp Hubble images allowed scientists to isolate the background source star and the lensing star in the foreground. There were two possible scenarios to explain the observations. One was a Saturn mass planet, and a Earth Mass planet orbiting a single star, or a Saturn mass planet orbiting a pair of red dwarfs. Further analysis revealed that the single gas giant orbiting a pair of red dwarfs was the only theory consistent with the observed data.
The use of gravitational microlensing to discover this planet opens up the possibility of using Hubble to discover even more exoplanets using this technique. So far the Kepler spacecraft has discovered ten exoplanets in orbit around binary star systems.