SCIENCE
10/28/2014 11:23 am ET Updated Oct 28, 2014

Astronomers Spot First Ice Giant Outside Our Solar System

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Astronomers have discovered the first "ice giant" outside our solar system--an exoplanet that looks a lot like the icy worlds in our own solar system, Uranus and Neptune.

The first-of-its-kind discovery may answer some big questions about how these strange planets formed the way they did--in our solar system and in others.

For instance, “nobody knows for sure why Uranus and Neptune are located on the outskirts of our solar system, when our models suggest that they should have formed closer to the sun,” Dr. Andrew Gould, an Ohio State University astronomer who was part of the research team that discovered the exoplanet, said in a written statement. “One idea is that they did form much closer, but were jostled around by Jupiter and Saturn and knocked farther out.”

The newfound ice giant orbits one star in a binary star system about 25,000 light-years from Earth. About four times more massive than Uranus, the exoplanet orbits its star at almost exactly the same distance as Uranus orbits our sun.

The researchers made the discovery via gravitational microlensing, an observational technique in which gravity from a star is used to magnify the light coming from a more distant star.

“Only microlensing can detect these cold ice giants that, like Uranus and Neptune, are far away from their host stars," Dr. Radek Poleski, a postdoctoral researcher at Ohio State University and the leader of the team that made the discovery, said in the statement. "This discovery demonstrates that microlensing is capable of discovering planets in very wide orbits... 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."

A paper describing this discovery was published online in The Astrophysical Journal on October 13, 2014.

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