UT astronomer helps locate previously unknown exoplanet

It’s not every day an astronomer discovers a new planet, but one studying at the University of Texas did just that recently with the help of a learning computer at Google.

NASA said Thursday that UT-Austin’s Andrew Venderburg and Google’s Christopher Shallue located a previously undiscovered planet orbiting Kepler-90, a sun-like star 2,545 light years from Earth in the constellation Draco. The new planet, designated Kepler-90i, marks the eighth planet found around the star, tying our system as having the highest number of known planets.

“For the first time since our solar system planets were discovered thousands of years ago, we know for sure that our solar system is not the sole record holder for the most planets,” said Vanderburg, a NASA Sagan Postdoctoral Fellow and astronomer at UT.

Kepler-90i is much closer to its home star than Earth is to our sun. It is believed to be around 30 percent larger than Earth and orbits Kepler-90 every 14.4 days. Kepler-90i is so close to its star that the surface temperature is theorized to be 800°F (similar to the surface temperature of Mercury). Kepler-90h, the outermost planet in the system, is a gas giant around the size of Jupiter that orbits its star at a similar distance between Earth and the sun. That planet orbits around Kepler-90 every 331.6 days.

“The Kepler-90 star system is like a mini version of our solar system. You have small planets inside and big planets outside, but everything is scrunched in much closer,” Vanderburg said.

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Vanderburg and Shallue, a Google machine learning researcher, trained a computer to identify signs of an exoplanet in light readings recorded from NASA’s Kepler space telescope. NASA said the pair trained the computer to identify exoplanets during their orbits in a set of 15,000 previously vetted signals from Kepler. They then used the “neural net” to examine data from 670 star systems with multiple known exoplanets.

"Machine learning really shines in situations where there is so much data that humans can't search it for themselves," Shallue said.

“We got lots of false positives of planets but also potentially more real planets,” Vanderburg said. “It’s like sifting through rocks to find jewels. If you have a finer sieve, then you will catch more rocks, but you might catch more jewels as well.”

NASA said the work by Vanderburg and Shallue also located a sixth exoplanet in the Kepler-80 system, dubbed Kepler-80g. Their findings will be published in the Astronomical Journal, and NASA said Shallue and Vanderburg plan to apply their neural network to Kepler’s full set of more than 150,000 stars.

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