They’re hot, they’re huge and they move the wrong way. In the rapidly growing catalog of planets found outside the solar system, about a dozen Jupiter-sized ones tightly circle their stars in the wrong direction. Now scientists have come up with an explanation for these wrong-way worlds that should help astronomers better understand how planets interact and might even lead to the discovery of more exoplanets.
Scientists believe they have a pretty good handle on how planets form. When a star is born, it is surrounded by a swirling cloud of gas and dust that moves in the same direction as the star’s rotation, pretty much in line with the stellar equator. Over millions of years those dust grains gradually stick together, growing larger and larger until one or more planets have cleared their own orbital paths. Since the original material was orbiting in the same direction as the star’s rotation, every planet should do so as well.
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