International planet hunters reveal vast catalog of strange worlds

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The artist’s conception of 126 planets in the latest TESS-Keck Survey catalog is based on data such as the planet’s radius, mass, density and temperature. Question marks represent planets that require more data for full characterization. Credit: WM Keck Observatory/Adam Makarenko

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The artist’s conception of 126 planets in the latest TESS-Keck Survey catalog is based on data such as the planet’s radius, mass, density and temperature. Question marks represent planets that require more data for full characterization. Credit: WM Keck Observatory/Adam Makarenko

Although thousands of planets have been discovered around other stars, relatively little is known about them. A NASA catalog of 126 exotic, newly discovered worlds contains detailed measurements that allow comparisons with our own solar system.

The catalog describes a fascinating mix of planet types beyond our solar system, from rare worlds with extreme environments to worlds that could potentially support life.

The planets were analyzed by a large, international team of scientists using NASA’s Transiting Exoplanet Survey Satellite (TESS) in collaboration with the WM Keck Observatory on Maunakea, Hawaii. They are described in the current edition of The Astrophysical Journal Supplement Series.

‘Relatively few of the previously known exoplanets have both mass and radius measurements. The combination of these measurements tells us what the planets might be made of and how they formed,” said Stephen Kane, a UC Riverside astrophysicist and principal investigator at the research center. the TESS-Keck survey.

“With this information, we can begin to answer questions about where our solar system fits in the grand tapestry of other planetary systems,” Kane said.

The research team worked on the catalog for three years. They analyzed more than 13,000 radial velocity (RV) measurements to calculate the masses of 120 confirmed planets, plus six candidate planets, spread across the northern sky.

Although the planets themselves are not visible, they do have a visible effect. As they orbit Earth, the planets pull on their host stars, causing them to “wobble.” When the star moves toward a telescope, the visible light becomes slightly bluer; when it moves away from us, the light becomes slightly redder.

This is very similar to how sound behaves. Due to the Doppler effect, a fire truck’s siren sounds higher as it gets closer and lower as it drives away.

“These RV measurements allow astronomers to detect and learn the properties of these exoplanetary systems. If we see a star regularly wobble back and forth, we can infer the presence of a planet in orbit and measure the planet’s mass,” says Ian Crossfield, University of Kansas. astrophysicist and co-author of the catalogue.

Several planets in the TESS-Keck Survey stand out as touchstones for deepening astronomers’ understanding of the diverse ways planets form and evolve.

A related research article published in The astronomical magazine and written by UCR student Michelle Hill announces the discovery of two new planets orbiting a star like our sun. The first is a “sub-Saturn” planet with a mass and radius intermediate between that of Neptune and Saturn.

“There’s an ongoing debate about whether planets below Saturn are really rare, or whether we’re just bad at finding planets like this,” Hill said. “So this planet, TOI-1386 b, is an important addition to this demographic of planets.”

TOI-1386 b takes just 26 days to orbit its star. Meanwhile, its neighbor, a planet with a mass close to that of Saturn, takes 227 days to orbit the same star.

Another research paper written by UCR graduate student Daria Pidhorodetska and available on the arXiv preprint server describes a planet about half the size of Neptune that takes just 19 days to orbit its star, which is very similar to our Sun.

“Planets smaller than Neptune but larger than Earth are the most common worlds in our Milky Way, yet they are absent from our own solar system. Every time a new one is discovered, we are reminded how diverse our universe is, and that our existence in the cosmos may be more unique than we can understand,” Pidhorodetska said.

There are many stars that don’t look like our sun. If scientists want to make good comparisons between our world and others, they need to find stars of similar age, size and mass. “Then we can compare apples to apples,” Kane said. “That’s the exciting part about the articles produced by Michelle and Daria, because they make this possible.”

Planets with even more extreme, ultra-short orbits around stars, unlike our Sun, are also described in detail in the catalogue. One is so close to its orange dwarf star that it completes its orbit in less than twelve hours.


TOI-1798, a two-planet system. The inner planet is a strange Super-Earth so close to its star that a year on this alien world is only half an Earth day. Credit: WM Keck Observatory/Adam Makarenko

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TOI-1798, a two-planet system. The inner planet is a strange Super-Earth so close to its star that a year on this alien world is only half an Earth day. Credit: WM Keck Observatory/Adam Makarenko

“TOI-1798 c orbits its star so quickly that a year on this planet lasts less than half a day on Earth. Because of their proximity to their host stars, planets like these are also ultra-hot and receive more than 3,000 times the radiation that Earth receives from the sun,” said Alex Polanski, a physics and astronomy graduate student at the University of Kansas and lead author of the catalog article.

“Existing in this extreme environment means that this planet has likely lost whatever atmosphere it initially formed,” Polanski said.

Ultimately, this new catalog represents an important contribution to both NASA’s TESS mission and to answering the question of whether other planets are capable of hosting life as we know it.

“Are we unusual? The jury is still out on that, but our new mass catalog represents an important step toward answering that question,” Kane said.

More information:
Polanski et al. The TESS-Keck survey. XX. 15 new TESS planets and a uniform RV analysis of all research objectives The Astrophysical Journal Supplement Series(2024). DOI: 10.3847/1538-4365/ad4484, iopscience.iop.org/article/10. …847/1538-4365/ad4484

Michelle L. Hill et al., The TESS–Keck Survey. XIX. A warm, transiting planet with less mass than Saturn and a non-transiting planet with Saturn’s mass orbiting a solar analog, The astronomical magazine (2024). DOI: 10.3847/1538-3881/ad2765

Daria Pidhorodetska et al., The TESS-Keck survey. XXII. A sub-Neptune orbiting TOI-1437, arXiv (2024). DOI: 10.48550/arxiv.2405.12448

Magazine information:
arXiv

Astronomical magazine

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