NASA's planet-hunter TESS finds its first earth-sized world

NASA’s planet-hunting spacecraft Transiting Exoplanet Survey Satellite (TESS) has discovered its first Earth-size world orbiting a star located about 53 light years away. The star, HD 21749a, also hosts at least one other world, a warm “sub-Neptune” planet with a mass about 23 times that of Earth and a radius about 2.7 times larger. The new world is likely rocky and circles very close to its star, completing one orbit in just under eight days. The planet is likely very hot, with surface temperatures perhaps as high as 800 degrees F (427 degrees C).

"It's so exciting that TESS, which launched just about a year ago, is already a game-changer in the planet-hunting business," Johanna Teske, author of a study describing the planets and Hubble Postdoctoral Fellow at the Carnegie Institution for Science, said in a statement. "The spacecraft surveys the sky and we collaborate with the TESS follow-up community to flag potentially interesting targets for additional observations using ground-based telescopes and instruments." The study was published in The Astrophysical Journal Letters on Monday.

The TESS was launched on April 18, 2018. It detects exoplanets by measuring the slight dimming of a star’s light when a planet moves across the disc as viewed from Earth. The PFS was used to compute the mass of the sub-Neptune world by precisely measuring the very slight wobble in the host star’s position caused by the tug of the planet’s gravity. “PFS is one of the only instruments in the Southern Hemisphere that can do these types of measurements,” Teske said. “So, it will be a very important part of further characterising the planets found by the TESS mission.”

NASA expects TESS to allow for the cataloging of more than 1,500 exoplanets, but it has the potential to find thousands. Of these, officials anticipate, 300 will be Earth-size exoplanets or double-Earth-size super Earths.