Our galaxy may have acquired some new real estate.
NASA has discovered an Earth-size planet orbiting around a faraway star — and it could be habitable.
Dubbed TOI 700 e, the exoplanet is the fourth discovered in the TOI 700 system, at 100 light-years away.
The research team presented the result at the 241st meeting of the American Astronomical Society in Seattle on Tuesday.
TOI 700 is the small, cool dwarf star at the center of the system, home also to the recently discovered planets TOI 700 b, c and d. But just two out of the four planets, d and e, fall in the habitable “goldilocks” zone, where the distance between the planet and star is at a point that can sustain liquid water — meaning the conditions could be right for life.
“This is one of only a few systems with multiple, small, habitable-zone planets that we know of,” Emily Gilbert, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory in Southern California who led the work, said in a statement.
The scientists used data from NASA’s Transiting Exoplanet Survey Satellite (TESS) to identify the new planet, which is 95% of Earth’s size and likely rocky. Planet e takes 28 days to orbit its star, while d has a 37-day orbit.
The innermost planet, b, is about 90% of Earth’s size and is on a 10-day orbit around the star. TOI 700 c is over 2.5 times bigger than Earth and orbits the star every 16 days.
The researchers believe the planets are probably tidally locked, meaning they only spin once per orbit, so one side always faces the star — similar to how Earth only sees one side of the Moon.
Finding other systems with Earth-sized planets can actually help scientists learn more about our own solar system, and demonstrates why continued study of the TOI 700 system is important for future insights.
“That makes the TOI 700 system an exciting prospect for additional follow-up. Planet e is about 10% smaller than planet d, so the system also shows how additional TESS observations help us find smaller and smaller worlds,” Gilbert explained.
TESS, designed to detect far-flung planets and stars, has four cameras that allow it to see 85% of the sky while searching for exoplanets orbiting stars less than 300 light-years away. It monitors large portions of the sky, also known as sectors, for about 27 days at a time, allowing it to track any alterations in brightness caused by a previously unobserved planet crossing over its star.
TESS was originally on a two-year mission that started in 2018 to observe the southern and northern sky, but returned to the southern sky in 2020 for an extra year — which was when the new planet was discovered.
“TESS just completed its second year of northern sky observations,” said Allison Youngblood, a research astrophysicist and the TESS deputy project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “We’re looking forward to the other exciting discoveries hidden in the mission’s treasure trove of data.”
The extra year of TESS also allowed scientists to recalculate previous findings and ascertain planet sizes, which ended up being about 10% smaller than they originally thought.
“If the star was a little closer or the planet a little bigger, we might have been able to spot TOI 700 e in the first year of TESS data,” said Ben Hord, a graduate researcher at Goddard. “But the signal was so faint that we needed the additional year of transit observations to identify it.”
Since TESS’ launch, it’s discovered more than 260 “confirmed” exoplanets, along with 4,000 “candidates” remaining to be verified. About 1,700 potential candidates have been ruled out.
More than 5,000 exoplanets have been discovered and “confirmed” by NASA out of the billions that exist in our Milky Way galaxy alone.
In 2022, over 300 exoplanets were identified, including water worlds and a burgeoning gas giant, as well as TOI 3757 b, an exoplanet that’s slightly bigger than Jupiter, yet carries the density of a marshmallow.