International planet hunters uncover a vast catalog of strange worlds

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

The catalog details a fascinating mix of planet types outside our solar system, from rare worlds with extreme environments to those that could 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 at Maunakea, Hawaii. They are described in today’s edition The Astrophysical Journal Supplement Series.

“Relatively few 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 of the TESS-Keck survey.

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

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

Although the planets themselves are not visible, they have a visible effect. As they orbit, the planets pull on their host stars, causing them to “wobble”. As the star moves toward the telescope, its visible light turns blue; as it moves away from us, the light shifts slightly to the red.

It’s similar to how sound behaves. Due to the Doppler effect, the fire engine’s siren sounds louder as it approaches and quieter as it moves away.

“These RV measurements allow astronomers to detect and learn the properties of these exoplanetary systems. When we see a star rocking back and forth regularly, we can infer the presence of an orbiting planet and measure the planet’s mass,” said Ian Crossfield, University of Kansas. astrophysicist and co-author of the catalog.

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

A related research paper published in The Astronomical Journal and authored by UCR graduate 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 between Neptune and Saturn.

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

TOI-1386 b takes only 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 overview document authored by UCR graduate student Daria Pidhorodetska and available at arXiv preprint server, describes a planet 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 galaxy, yet they are absent from our own solar system. Every time a new one is discovered, we are reminded of how diverse our universe is and that our existence in space can be more unique, than we can understand,” said Pidhorodetska.

There are many stars that are not like our sun. If scientists want to properly compare our world to 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 of the paper that Michelle and Daria have created, because they make it possible.

The catalog also details planets with even more extreme, ultra-short orbits around stars unlike our Sun. One is so close to its orange dwarf star that it completes an orbit in less than 12 hours.

“TOI-1798 c orbits its star so fast that one year on this planet takes less than half an Earth day. Planets like this are also very hot due to their proximity to their host stars – receiving more than 3,000 times more radiation .” that the Earth receives from the Sun,” said Alex Polanski, a graduate student in physics and astronomy at the University of Kansas and lead author of the catalog.

“Existence in this extreme environment means that this planet has probably lost all the atmosphere it originally formed,” Polanski said.

Ultimately, this new catalog represents a significant contribution both to 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 bulk catalog is a significant step toward answering that question,” Kane said.