A new catalog of 126 worlds beyond the solar system contains a cornucopia of newly discovered planets; some have extreme and exotic natures, but others could potentially support life as we know it.
The catalog’s mix of planets is further evidence of the vast and wild diversity of worlds beyond our cosmic backyard; It even shows that our solar system is perhaps a little boring. Yet, although these planets are very different from Earth and their neighbors, perhaps they can help us better understand why our planetary system looks the way it does, thus revealing our place in the wider universe.
The catalog of extrasolar planets, or “exoplanets,” was created using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) in collaboration with the W. M. Keck Observatory in Hawaii.
“With this information, we can begin to answer questions about where our solar system fits into the larger fabric of other planetary systems,” said TESS-Keck Survey Principal Investigator Stephen Kane, an astrophysicist at the University of California, Riverside. expression.
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The new TESS-Keck Survey of 126 exoplanets is truly different from previous exoplanet surveys because it contains complex data on the majority of the planets included.
“Relatively few of the previously known exoplanets have measurements of both mass and radius,” added Kane. “The combination of these measurements tells us what planets might be made of and how they form.”
“Seeing red” to measure exoplanet masses
The catalog was created over the course of three years, with the team using 13,000 measurements of tiny “wobbles” caused by planets as they orbit their stars and exert a small gravitational pull on them. This tug causes a star to first move slightly further away, then move slightly towards Earth.
When stars move slightly further away, this lengthens the wavelengths of light they emit, moving them towards the “red end” of the electromagnetic spectrum. When stars move toward Earth, the wavelength of the light they emit is compressed slightly, making it “bluer.”
This use of redshift and blueshift by astronomers is called the “radial velocity method.” This is a good way to determine mass, since the strength of the gravitational pull a planet exerts on a star is proportional to its mass. Thus, the radial velocity method allowed Kane and his team to determine the masses of 120 confirmed exoplanets and six exoplanet candidates.
“These radial velocity measurements allow astronomers to detect and learn about the properties of these exoplanet systems,” said Ian Crossfield, a University of Kansas astrophysicist and co-author of the catalogue. “When we see a star regularly wobbling back and forth, we can infer the presence of a planet in orbit and measure the planet’s mass.”
Excitingly, some of the 126 exoplanets in the TESS-Keck Survey may deepen astronomers’ understanding of how a range of different planets form and evolve.
A strange super-Earth, a sub-Saturn and more!
Two of the new planets in the TESS-Keck Survey orbit a sun-like star called TOI-1386, located about 479 light-years away.
The mass and width of one of these exoplanets places it somewhere in the solar system between the gas giant Saturn and the smaller, less massive ice giant Neptune. This makes this planet, designated TOI-1386 b, a “sub-Saturn” planet and a fascinating target for planetary scientists.
“There is an ongoing debate about whether planets beneath Saturn are truly rare or whether we are just bad at finding such planets,” explorer and UCR graduate student Michelle Hill said in the statement. “So planet TOI-1386 b is an important addition to this planetary demographics.”
Located at a distance from its parent star equivalent to about 17% of the distance between Earth and the sun, TOI-1386 b takes only 26 Earth days to complete one orbit.
Its newly discovered closest neighbor is a little quieter. TOI-1386 c is a bloated gas giant that is as large as Jupiter but has only 30% the mass of the largest planet in the solar system. It is about 70% the distance between Earth and the sun from its parent star and has a year lasting about 228 Earth days.
Another fascinating world among this group of exoplanets is about half the size of Neptune, more than ten times the mass of Earth, orbiting TOI-1437 (also known as HD 154840) and located about 337,000 light-years away.
The sub-Neptunian planet, called TOI-1437 b, orbits its star at a distance of about 14% of the distance between Earth and the sun and has a year lasting about 19 Earth days. Discovered by TESS due to the small dip in light it causes as it passes across the surface of its star, TOI-1437 b is one of the few sub-Neptunes known to pass past its star with a well-defined mass and radius.
TOI-1437 b also highlights an interesting absence in our cosmic backyard.
“Planets smaller than Neptune but larger than Earth are the most common worlds in our galaxy, but they are absent from our own solar system,” discovery and UCR graduate student Daria Pidhorodetska said in a statement. she said. “Every time something new is discovered, we are reminded of how diverse our universe is and how our existence in it may be more unique than we can understand.”
Another interesting exoplanet detailed for the first time in this new catalog is TOI-1798 c, a super-Earth orbiting an orange dwarf star whose year lasts only 12 Earth hours.
“A year on this planet lasts less than half a day on Earth,” said study lead author Alex Polanski, a graduate student in physics and astronomy at the University of Kansas. “Due to their proximity to their host stars, planets like these are also extremely hot; they receive more than 3,000 times the radiation that Earth receives from the sun.”
This makes the TOI-1798 planetary system, which also hosts a sub-Neptunian planet that completes its orbit in about eight days, one of only a few star systems known to have an inner super-Earth planet with an ultrashort period (USP). ) orbit.
“While the majority of planets we know today revolve around their star faster than Mercury orbits the sun, USPs take this to the extreme,” Pidhorodetska added. “TOI-1798c orbits its star so fast that a year on this planet lasts less than half a day on Earth. Because of their proximity to their host star, USPs are also extremely hot; they receive more than 3,000 times the radiation that Earth receives. This is extreme.” “existing in the environment means that this planet has probably lost the atmosphere it originally formed.”
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The publication of the TESS-Keck Survey Mass Catalog means astronomers now have the opportunity to explore in depth the work of TESS, which launched in April 2018, and measure how it is changing our understanding of exoplanets.
With thousands of planets just confirmed from the TESS mission alone, the publication of exoplanet catalogs like this will also become more common.
“Are we unusual? The jury is still out on that, but our new collective catalog represents a major step towards answering that question,” said Kane.
The outer planets are described in the Thursday, May 23 issue of The Astrophysical Journal Supplement.