Youngest planet spotted around alien star

Image: K2-33b
An artist’s conception shows K2-33b crossing the disk of its parent star. (Credi: NASA / JPL-Caltech)

Scientists say they’ve detected a giant planet circling a star that’s only 5 million to 10 million years old, which would make it the youngest exoplanet ever identified.

The super-Neptune-sized planet traces a super-close-in orbit, making a complete swing around its parent star every 5.4 Earth days, according a team of astronomers associated with NASA’s repurposed Kepler space telescope. The star, known as K2-33, is in the Upper Scorpius stellar association, about 500 light-years from Earth.

Infrared observations of K2-33 indicate that the star is still surrounded by the remnants of gas and dust from a protoplanetary disk. Such disks form around stars as they’re born and give rise to planets, but the disks are thought to dissipate after a few million years. That’s how astronomers figured out that the planet was so young.

“At 4.5 billion years old, the Earth is a middle-aged planet — about 45 in human-years,” Caltech astronomer Trevor David said in a news release. “By comparison, the planet K2-33b would be an infant of only a few weeks old.”

David is the first author of a paper on the discovery published online today by the journal Nature.

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By Alan Boyle

Mastermind of Cosmic Log, contributing editor at GeekWire, author of "The Case for Pluto: How a Little Planet Made a Big Difference," president of the Council for the Advancement of Science Writing. Check out "About Alan Boyle" for more fun facts.

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