BYU researchers help discover massive exoplanet

Clement Gaillard spent three or four nights a week operating BYU’s Orson Pratt Observatory telescope in the summer of 2015. On the night of June 23, the physics undergrad pointed the telescope toward a star more than a thousand light years away, recording meticulous data and hoping. Soon after, physics professor Denise Stephens and a visiting student reduced the data and looked anxiously at the plot points they had gathered. On a six-hour timeline, the dots congregated along a straight line for two hours, dipped down for two, then popped back up through the end.

The “huge, beautiful baseline” they saw, said Stephens, hinted at what would soon be confirmed by a partnering institution: they had helped discover a massive exoplanet. The dip on their chart came when the star they observed was briefly shadowed by that planet.

KELT-16b is one of 19 exoplanets identified over the past four years by the Kilodegree Extremely Little Telescope (yep, that’s its real name) research group. Stephens and BYU physics professor Michael Joner, along with five BYU students, coauthored the 16b discovery paper, recently published in The Astronomical Journal.

Though time often slowed on those long nights of data gathering, Gaillard said, the opportunity to be a part of the project was a thrill. “Through a telescope, the night sky seems vast and uncharted,” he said — but the area of sky around their observation targets quickly became familiar. “I would consider this little part of the universe to be my research lab.”

As project architects on the 20-univeristy KELT team, which includes Vanderbilt, Ohio State and Caltech, Stephens and Joner have been tasked with evaluating exoplanet candidates identified by KELT’s two little telescopes. Stephens, observing from the top of campus’ Eyring Science Center; and Joner, observing from the West Mountain Observatory south of Utah Lake, have spent many a late night looking for those telling shadows on distant stars that would indicate the presence of transiting planets.

Unlike the seven Earth-like exoplanets recently unveiled by NASA, KELT-16b “is as different from Earth as you could possibly get,” said Joner.

For one, there’s the matter of temperature. The newly discovered gaseous planet has migrated “really, really close to its star,” said Joner: it’s now 50 times closer to its star than Earth is to its sun. So the planet is hotter than any planet in our solar system, with an estimated average temperature of more than 4,000 degrees Fahrenheit. As such, said Joner, it “would have all kinds of weird atmospheric physics going on.”

Then there’s the size: KELT-16b clocks in with a diameter 15 times that of Earth and nearly 1.5 times that of Jupiter. The heat, gaseous atmosphere and size combined put 16b in a category of exoplanets called hot Jupiters.  

Hot Jupiters have lately caught the attention of planetary scientists, who are exploring their formation, movement and atmospheres. KELT-16b is a relatively young planet: “relatively” being the operative word in all numbers planetary. By way of comparison, Earth’s sun is 4.5 billion years old; 16b and its star are 3 billion years old. And based on its migration, the KELT research team estimate it will be “tidally shredded” (epic science-speak for “ripped apart after it runs into its star”) in “a mere” few hundred thousand years.

In the meantime, Stephens and Joner anticipate KELT-16b becoming a top exoplanet observation target for a number of reasons. Among them: 16b can be imaged by both the Hubble Telescope and NASA’s soon-to-be-launched James Webb Space Telescope, allowing scientists to observe the unique atmosphere. Additionally, 16b has an orbital period of less than a day, which makes its observation easier than a planet whose orbit takes weeks, months or years.

The KELT project will likely continue for a few more years, and Joner and Stephens will be listed as authors on all of the team’s planetary discovery papers. As they continue looking to the skies, said Stephens, “it’s fun to think about the universal question: are we alone out here? Everything we learn from the KELT research is exciting and getting us closer to finding a planet that looks a little bit more like Earth.”


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