Hawaii doctoral student confirms exoplanet

It took 10 years, but the first exoplanet candidate discovered by NASA’s Kep­ler Space Telescope has been confirmed as a genuine planet by an international team of astronomers led by a University of Hawaii graduate student.

The UH Institute for Astronomy’s Ashley Chontos announced the finding last week at the fifth Kepler/K2 Science Conference in Glendale, Calif.

“It’s very exciting,” the second-year doctoral student said in a phone interview. “When I started this I was fascinated by exoplanets, but I didn’t know I would discover one. It’s like, ‘Somebody pinch me.’”

Wednesday was the 10th anniversary of the launch of the NASA planet-hunting telescope, whose mission came to an end in 2018. During its decade of operation, Kepler discovered more than 2,000 exoplanets — planets that orbit stars outside our solar system.

Kepler found its exoplanets via the transit method, which records a dimming of brightness to indicate a planet is passing in front of a star. These dips in brightness allow researchers to calculate a planet’s characteristics, including size and orbital distance.

But further analysis was always needed to confirm them as genuine planets.

While Kepler-1658b was the first exoplanet candidate discovered by the space telescope, circumstances prevented it from being recognized as a planet.

For one, its initial size estimate was off. The size of both the planet and its star were greatly underestimated. Because the numbers not adding up, it was relegated to the “false positive” file.

Then Kepler recalibrated its data, and Chontos began reanalyzing Kepler host stars as part of her first-year graduate research project. Her IFA graduate advisor, Dan Huber, spotted the Kepler-1658b data discrepancies and suggested Chontos take a closer look.

Using an updated technique involving stellar sound waves, Chontos was able to demonstrate that both the planet and its star are in fact three times larger than previously estimated.

Further analysis was provided by Dave Latham, a prominent Smithsonian Astrophysical Observatory astronomer and pioneer in exoplanet exploration. His team collected the spectroscopic data that clearly demonstrated that Kepler- 1658b was a planet, Chontos said.

It turns out Kepler-1658b is an extremely hot, Jupiter- like world that orbits very close to its star — even closer than Mercury does to our sun, Chontos said. And Kepler-1658 circles an “evolved star” — a redder, bigger future version of our sun — closer than any other known planet and in less than four days.

If you were to stand on the planet, the star would appear 60 times larger in diameter than the sun as seen from Earth.

There are only about 20 planets similar to Kepler-1658 known to orbit evolved stars, Chontos said, and the latest discovery offers new insight into a phenomenon in which planets are engulfed by their host stars. The process appears to be much slower than previously thought, she said, and might not be the primary reason for the lack of planets around more evolved stars.

Chontos, who is pursuing a career in astronomy after seven years as a New York City fashion model, will now spend four months studying exoplanets with Sara Seager, a Massachusetts Institute of Technology astronomer and planetary scientist who is deputy science director of Transiting Exoplanet Survey Satellite, which will add to Kepler’s legacy by searching for exoplanets around stars closer to Earth.

It’s likely Chontos’ UH doctoral thesis will involve exoplanet research related to her TESS experience, she said.