Big Baby Moving Close and Fast

Caltech finds clues from young exoplanet, giving hints about what early Earth might have been like.


Using the Kepler Space Telescope and the Keck Observatory in Hawaii, astronomers from Caltech have identified the youngest exoplanet thus far discovered.  Dubbed K2-33b, it orbits a star about 500 light years away – and it’s only 5-10 million years old, an infant compared to the large majority of other known exoplanets.  The object is about the size of Neptune and it whizzes all the way around the star every five days.  Analysts say K2-33b’s star is still surrounded by a thin disc of planetary debris, indicating that it is nearing the end of its planet-forming phase.

One of K2-33b’s mysteries is that its orbit is very close to the star – only one-tenth of the distance that Mercury is from the Sun.  The fact that it is so hot and close is not particularly unusual, and analysts have previously theorized that such large planets move into close orbits from farther out in star systems over the course of hundreds of millions of years.  But, because it is so young, K2-33b seriously challenges that explanation.  To account for this new observation, astronomers posit two possibilities:  one, it might have drifted closer to the star in only a few hundred thousand years in a process called “disc migration”; or two, the planet may have formed right there in the orbital slot in which it was found.

“The newborn planet will help us better understand how planets form, which is important for understanding the processes that led to the formation of the Earth.”  -- Erik Petigura, Caltech

The Caltech study was published online yesterday in the journal Nature.

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