Last October, NASA’s planet-hunting Kepler space telescope took its final bow after uncovering over 2,600 alien worlds during almost a decade in space. But that doesn’t mean the search for exoplanets has stopped—in fact, things are just heating up. Dennis Overbye at The New York Times reports that Kepler’s successor, the Transiting Exoplanet Survey Satellite (TESS), that was launched last April has begun sending back data, including more than 200 potential planets with at least three new worlds already confirmed.
TESS finds planets the same way Kepler did, using the transit method to detect their signal. When a planet passes in front of its star, it creates a tiny dip in the intensity of the star’s light, which astronomers can use to estimate the size and orbit of the planet. While Kepler stared deeply at one spot in space, TESS will cover the entire 360-degree expanse of the sky during its two-year mission.
The new candidate planets were announced at the annual meeting of the American Astronomical Society in Seattle. These celestial bodies come from the first four segments of sky that TESS has scanned since officially beginning its mission in July. Lisa Grossman at Science News reports that some of the latest exoplanets are “downright strange.”
One, dubbed HD 21749b, orbits dwarf star HD 21749 in the constellation Reticulum just 52 light-years away. It takes about 36 Earth-days to orbit its sun, the longest orbital period of any nearby planet observed so far. It’s also the coolest (temperature-wise) nearby planet they’ve found, but that doesn’t mean it’s habitable.
HD 21749b is 2.84 times Earth’s size with a mass 23.2 times that of our planet, suggesting it has a thick atmosphere that is probably not conducive to life. And “cool” is a relative term: the planet is still 300 degrees Fahrenheit. Most of the planets close enough for us to observe are typically flame-roasted by their stars, so in comparison that’s balmy weather.
Lucy Campbell at The Guardian reports there are other interesting finds in the data as well. The planet-hunter also detected a planet circling the same dwarf star that appears to be Earth-size or smaller. If confirmed, it would be a target for more investigation.
“I’m very interested to know whether [it] has an Earth-like density to match its Earth-like radius – this will contribute to our understanding whether Earth-sized planets have diverse compositions or are all roughly similar to Earth,” says Johanna Teske, part of the TESS team and a Hubble postdoctoral fellow at the Carnegie Observatories in Pasadena, California.*
According to a press release, the space telescope also found a planet orbiting a star called Pi Mensae that’s similar in size and brightness to our sun. Previous studies found a large planet ten times the size of Jupiter orbiting the star called Pi Mensae b, but TESS discovered a new planet, Pi Mensae c, which has an almost circular orbit.
The other confirmed planet is the rocky LHS 3884b, which is about 1.3 times the size of Earth and just 49 light years away in the constellation Indus. But the planet orbits so closely to its star—an M-type dwarf about one-fifth the size of our sun—that it likely forms pools of lava during the day. Six supernovae that appeared in distant galaxies were also found by TESS and confirmed by ground-based telescopes.
These first findings are really just an appetizer. TESS has only examined four of the planned 26 segments of sky it will survey over next year and a half, staring for 27 days at roughly 200,000 stars per segment. If Kepler’s mountain of data is any indication, TESS should have plenty more surprises for us.
“We’re only halfway through Tess’s first year of operations and the data floodgates are just beginning to open,” TESS principal investigator George Ricker of MIT says in the release. “When the full set of observations of more than 300 million stars and galaxies collected in the two-year prime mission are scrutinized by astronomers worldwide, TESS may well have discovered as many as 10,000 planets, in addition to hundreds of supernovae and other explosive stellar and extragalactic transients.”
*Editor’s Note, January 14, 2019: A previous version of this article misstated Johanna Teske's title and affiliation as “Hubble fellow at MIT’s Kavli Institute for Astrophysics and Space Research” when it should be “a Hubble postdoctoral fellow at the Carnegie Observatories in Pasadena, California.” The article has since been updated to reflect this correction.