The planet orbits one member of a binary star system 25,000 light-years from Earth.
According to an Ohio State University (OSU) statement, a team led by OSU researcher Radek Poleski has discovered the first exoplanet that resembles the planet Uranus in our own solar system. The exoplanet falls into the category of ‘ice giants’, and adds another type of world to the exoplanet roster, which already includes rocky planets similar to Earth and gas giants akin to Jupiter.
The exoplanet is located in a binary star system approximately 25,000 light-years away in the direction of the constellation Sagittarius. One of the member stars is about two-thirds the mass of the Sun, while the other is about one-sixth as massive. The exoplanet itself is four times the mass of Uranus and orbits the larger of the two stars at nearly the same distance as Uranus revolves around the Sun.
The exoplanet and its home star system were found with the 1.3-meter Warsaw Telescope at Las Campanas Observatory in Chile, in the course of the Optical Gravitational Lensing Experiment (OGLE). The star system was discovered in light magnified by an intervening gravitational microlens, and object between Earth and the star system; the light from the more distant object, the binary system in this case, is magnified by the gravity of the microlensing object.
It was actually two separate microlensing events, one in 2008 and the other in 2010, that revealed the existence of the binary system and its ice giant planet. OGLE’s database currently includes 13,000 microlensing events; Poleski is designing software to scrutinize the database for indications of additional exoplanets in other solar systems.
“Only microlensing can detect these cold ice giants that, like Uranus and Neptune, are far away from their host stars. This discovery demonstrates that microlensing is capable of discovering planets in very wide orbits,” Poleski explained.
“We were lucky to see the signal from the planet, its host star, and the companion star. If the orientation had been different, we would have seen only the planet, and we probably would have called it a free-floating planet.”
The new research has been published online in The Astrophysical Journal.