NASA's TESS Discovered New Earth-size Exoplanet Orbiting Within the Habitable Zone of Its Star

NASA reports a newly discovered Earth-size exoplanet orbiting in the habitable zone at a nearby star. The American space agency presented its discovery during the 241st meeting of the American Astronomical Society, stating that the "Earth-sized" planet it just discovered is unique because it is the second such planet in a system orbiting a nearby star.

In its news release, NASA also mentions that this latest planet most likely has a "rocky" shell like Earth's, making both planets even more similar to each other.

NASA's TESS Discovered New Earth-size Exoplanet Orbiting Within the Habitable Zone of Its Star — Newly discovered Earth-size planet TOI 700 e orbits within the habitable zone of its star in this illustration. Its Earth-size sibling, TOI 700 d, can be seen in the distance. NASA/JPL-Caltech/Robert Hurt

Fourth Planet in Dwarf Star TOI 700

The planet is named TOI 700 e, which is most likely rocky and 95% the size of Earth. According to CNN, it is the fourth planet to be discovered around the tiny, cold M dwarf star TOI 700. NASA's Transiting Exoplanet Survey Satellite (TESS) mission discovered all of the exoplanets orbiting the nearby star

One of the planets in the system, TOI 700 d, was identified in 2020 and is the same size as Earth. Both of these exoplanets are in their star's habitable zone or are close enough to the star to have liquid water on their surfaces. The possibility of liquid water implies that the planets themselves may be, or may have been, hospitable for life.

Lead research author Emily Gilbert, a postdoctoral fellow at Jet Propulsion Laboratory at NASA said that the TOI 700 star system is among those few that they knew to possess tiny planets in habitable zones.

Gilbert added that this makes TOI 700 system an attractive prospect for follow-up research. More so, the TOI 700 e is around 10% smaller than planet d, which demonstrates how further TESS observations help in the discovery of small and smaller planets.

Small, cold M dwarf stars such as the TOI 700 are widespread in the cosmos, and many have been discovered to contain exoplanets in recent years. An example is the TRAPPIST-1 system and its seven exoplanets, which will be observed by the James Webb Space Telescope.

TOI 700 Star System and Its Planets

Among the planets in the TOI 700, planet b is the closest to the star and is about 90% the size of Earth and completes one fast circle around the star every 10 Earth days. Meanwhile, TOI 700 c is 2.5 times the size of Earth and completes one circle around the star every 16 days.

These planets are most likely tidally locked, which means they constantly face the same direction as the star, similar to how the same side of the moon always faces Earth.

Planets d and e in the star's habitable zone have longer orbits of 37 and 28 days, respectively, since they are a little further away from the star. The newly discovered Planet e is placed between planets c and d, as per JPL.

Scientists define the optimistic habitable zone as the range of distances from a star where liquid surface water may exist at some stage in a planet's history. The zone spans on either side of the conservative habitable zone, which is the region in which experts believe liquid water might remain throughout the majority of the planet's lifespan, wherein TOI 700 d and e orbits.

Finding additional systems in this region with Earth-sized worlds helps planetary scientists understand more about the history of our own solar system.