NASA’s Alien-Hunting TESS Telescope Finds First Earth-Like Planet Within the Habitable Zone
NASA reports that the Transiting Exoplanet Survey Satellite – or TESS – just returned data revealing its first Earth-like exoplanet that very well may be habitable.
Planet TOI 700 d is slightly larger than Earth (around 1.2 times the size) and takes just 37 days to orbit its host star. We know that it receives nearly as much light as Earth does – almost 86% – and, critically, it exists in the narrow margin known as the "habitable zone." This is the distance from a star at which a planet can support liquid water on its surface. The planet is also tidally locked to its star just like our Moon is to the Sun, which means that the same side is always facing the star (and is permanently in daylight).
The star this planet orbits – TOI 700 – is a red dwarf star just 100 light-years away in the constellation Dorado. It is approximately half the size of the Sun (and also has half its surface temperature). Scientists originally thought this star was the size of our Sun, which caused them to misclassify its planets as larger, hotter, and unable to support life.
"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," explained Emily Gilbert, a graduate student from the University of Chicago. "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."
Since the planet is tidally locked, any atmospheric conditions will look very different from what we know on Earth. Simulations so far show either a watery planet with a thick atmosphere or a cloudless sky over rocky terrain, with winds that always blow towards the host star.
"Someday, when we have real spectra from TOI 700 d, we can backtrack, match them to the closest simulated spectrum, and then match that to a model," said Gabrielle Engelmann-Suissa a visiting research assistant at NASA Goddard from the Universities Space Research Association who led the exoplanet modeling team. "It's exciting because no matter what we find out about the planet, it's going to look completely different from what we have here on Earth."