Let the grade-school jokes begin: Astronomers say they have detected the first known Uranus-like planet circling an alien star. The exoplanet is part of a double-star system that's 25,000 light-years from Earth, known as OGLE-2008-BLG-092L. Its presence was detected using a method known as microlensing, which takes advantage of the light-bending effect of massive stars to magnify faraway objects.
The newfound planet, reported by Ohio State University's Radek Poleski and his colleagues, is four times as massive as Uranus (heh, heh), and orbits at a similar distance (about 19 times farther away from its primary parent star than Earth is from the sun). Planets with masses in that range have been detected before, but not that far out. Ohio State's Andrew Gould, a co-author of the research paper appearing online in The Astrophysical Journal, said in a news release that the alien Uranus may help explain how our own solar system's ice giants ended up where they are:
“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. One idea is that they did form much closer, but were jostled around by Jupiter and Saturn and knocked farther out. Maybe the existence of this Uranus-like planet is connected to interference from the second star. Maybe you need some kind of jostling to make planets like Uranus and Neptune."
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— Alan Boyle
In addition to Poleski and Gould, the authors of "Triple Microlens OGLE-2008-BLG-092L: Binary Stellar System With a Circumprimary Uranus-Type Planet" include Jan Skowron, Andrzej Udalski, Cheongho Han, Szymon Kozłowski, Łukasz Wyrzykowski, Subo Dong, Michał K. Szymański, Marcin Kubiak, Grzegorz Pietrzyński, Igor Soszyński, Krzysztof Ulaczyk and Paweł Pietrukowicz.