The distance at which K2-33b orbits its parent star is already providing a critical insight to planetary migration models. With a 5 day orbit, the world is situated 20 times closer to its star than Earth is to the sun. Most planetary formation models predict gas giant worlds form far away from their star, like in our solar system. But there's a preponderance of "hot-Jupiters" orbiting other stars, i.e., large gas giant worlds with extremely compact, hot orbits.
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"After the first discoveries of massive exoplanets on close orbits about 20 years ago, it was immediately suggested that they could absolutely not have formed there, but in the past several years, some momentum has grown for in situ formation theories, so the idea is not as wild as it once seemed," said David.
So the question is: Did K2-33b form further away than it is now and, through an as-yet to be understood phenomenon, migrate very quickly to the inner star system? Or do planetary migration theories need to be re-thought and perhaps it is possible for gas giant exoplanets to form very close to their host stars? After all, K2-33b has literally just formed (on cosmic timescales), it seems most likely that it formed where it is now.
"In the last 20 years, we have learned that nature can produce a staggering diversity of planets -- from planets that orbit two stars to planets that complete a full orbit every few hours," added Petigura. "We have much to learn, and K2-33b is giving us new clues."
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Sources: Caltech, NASA/JPL