Scientists from the University of Chicago and other institutions around the world have discovered multiple new interesting worlds beyond Earth—including its first potentially habitable Earth-size world and another that is a ‘Star Wars’-type system with two suns.
The new exoplanets—planets beyond our solar system—were spotted with NASA’s new TESS satellite and announced Jan. 6 at the 235th American Astronomical Society meeting. In both cases, high school students helped find them.
Some world our own size
Even as scientists have discovered more and more planets in other star systems, ones that could sustain life similar to ours have remained fairly rare. The biggest flag scientists look for is the ability to maintain liquid water on the surface.
Launched in 2018, TESS is a space-based satellite specifically built to search for bright, nearby worlds close to the size of Earth. TESS tracks changes in stars’ brightness caused by orbiting planets crossing in front of their stars from our perspective, events called transits.
Its first habitable-zone Earth-size world is TOI 700 d, which orbits a small, cool M dwarf star located just over 100 light-years away in the southern constellation Dorado. It’s roughly 40% of the Sun’s mass and size and about half its surface temperature.
It was only discovered after a misclassification of the star was corrected, in part due to help from high school student Alton Spencer.
“When we corrected the star’s parameters, the sizes of its planets dropped, and we realized the outermost one was about the size of Earth and in the habitable zone,” said Emily Gilbert, a graduate student at the University of Chicago whose lab seeks to discover new worlds. “Additionally, in 11 months of data we saw no flares from the star, which improves the chances TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions.”
Researchers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, modeled 20 potential environments of TOI 700 d to gauge if any version would result in surface temperatures and pressures suitable for habitability.
Because TOI 700 d is tidally locked to its star, the planet’s cloud formations and wind patterns may be strikingly different from Earth’s.
One simulation included an ocean-covered planet with a dense, carbon-dioxide-dominated atmosphere similar to what scientists suspect surrounded Mars when it was young. The model atmosphere contains a deep layer of clouds on the star-facing side. Another model depicts TOI 700 d as a cloudless, all-land version of modern Earth, where winds flow away from the night side of the planet and converge on the point facing the star.
A Tatooine-like vision
When Luke Skywalker stood in the desert of the planet Tatooine and looked up at the sky, he watched not one sun set, but two. So would any potential inhabitants of a newly discovered world 1,300 light-years away from us. (Though it's thought to be a gas planet, so no one would be standing on it.)