Announced on January 6, 2020, NASA’s TESS mission has just discovered its first Earth-sized, habitable zone planet.
If it has an Earth-like atmosphere, it could possess liquid water on its surface.
TESS works by surveying different slivers of the sky one month at a time in succession.
The polar areas receive the greatest coverage, and include the region where the star TOI 700 is located.
Appearing in 11 independently viewed TESS sectors, TOI 700 possesses at least 3 planets orbiting it.
Although TOI 700 is an M-class red dwarf, it exhibits no flaring, benefitting potential lifeforms.
The third planet from the star — TOI 700d — is only 19% larger than Earth, receiving 86% of the incident energy on Earth.
Even though the planet is likely to be tidally locked, with the same face always towards its star, it’s still potentially habitable.
Everything depends on the composition of the atmosphere and how energy flows around the world.
A CO2-heavy atmosphere creates a uniformly hot world, where life is strongly disfavored.
For contrast, a cloudless, oceanless world with an Earth-like atmosphere possess sunward-directed winds and various temperature zones.
Technologies beyond James Webb will be required to determine its true composition.