Astronomers use Keck Observatory to create ‘catalog’ of exoplanets

CREDIT: W. M. KECK OBSERVATORY/ADAM MAKARENKO
An artist’s rendering of the exoplanets identified by the survey. The planets are not to scale, ranging from roughly Earth-sized at the top of the image, to Jupiter-sized at the bottom. Planets labeled with questions marks represent those that cannot be characterized without further data.

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CREDIT: W. M. KECK OBSERVATORY/ADAM MAKARENKO

An artist’s rendering of the exoplanets identified by the survey. The planets are not to scale, ranging from roughly Earth-sized at the top of the image, to Jupiter-sized at the bottom. Planets labeled with questions marks represent those that cannot be characterized without further data.

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Astronomers using a Mauna Kea observatory have published a “catalog” of more than 100 exoplanets.

A years-long survey using W.M. Keck Observatory was able to identify 126 confirmed and likely exoplanets — planets outside our solar system — from data collected by a NASA satellite.

“Surveys like this are really a labor of love,” said John O’Meara, deputy director and chief scientist at Keck. “It’s been going on for many years. It took more than 300 nights of Keck observation time.”

A team led by University of Kansas graduate student Alex Polanski analyzed data from the NASA Transiting Exoplanet Survey Satellite, or TESS. O’Meara explained that TESS operates by detecting “transits,” the blips that take place when an object passes between Earth and a distant star.

But while those transits allow astronomers to make a pretty educated guess that an exoplanet exists, they can’t tell much about the planet itself, O’Meara said.

Polanski’s team used an instrument at Keck to analyze more than 9,000 spectrographic fluctuations among the stars highlighted by TESS. These fluctuations, which O’Meara called wobbles, indicate the presence of an orbiting body exerting a gravitational pull on the host star — most likely a planet.

By analyzing the minute changes in these wobbles, O’Meara said astronomers are able to determine the mass of the orbiter. And, he said, with such a large data set to work with, some of the planets detected were bound to be unusual.

“It’s like if you sit in Grand Central Station long enough, eventually you’re bound to see a person who’s over 100 years old,” O’Meara said.

The catalog, published Thursday, specifically highlights two planets with especially odd characteristics. One, designated TOI-1824 b, is a planet nearly 19 times Earth’s mass but only about 2.6 times its size, making it unusually dense. Team members hypothesized that the planet’s density could stem from a water-rich core and an atmosphere of steam.

The other outlier planet, TOI-1789 c, is a “super-Earth” — a planet with a mass higher than Earth’s but substantially lower than planets like Uranus’ and Neptune’s — that O’Meara said is “just getting cooked.” The planet is so close to its sun, its year is only 12 hours long.

The other planets within the catalog are more typical, although O’Meara noted that the study makes up a not-insignificant fraction of all known exoplanets — only about 5,000 have ever been discovered.

“Sometimes it’s important to go after a wide group of things instead of just drilling down in depth on one object,” O’Meara said. “Because of this, we can learn a lot more about what exoplanets are like.”