Second possibly habitable planet the size of Earth found orbiting nearby star

A NASA mission has spotted an Earth-sized exoplanet orbiting a tiny star about 100 light-years away.

The planet, called TOI 700 e, is likely rocky and 95% the size of our world. The celestial body is the fourth planet to be detected orbiting the small and cool M dwarf star called TOI 700. All of the exoplanets were found by NASA’s Transiting Exoplanet Survey Satellite (TESS).

Another planet in the system, discovered in 2020 and called TOI 700 d, is also the size of Earth. Both exoplanets lie in their star’s habitable zone, or just the right distance for liquid water to possibly exist on their surfaces. The potential for liquid water suggests that the planets themselves could be, or may have been, habitable places for life.

The discovery of the fourth planet was announced on Tuesday (10) during the 241st meeting of the American Society of Astronomy in the city of Seattle, in the United States, and a study on the exoplanet was accepted for publication by the journal “The Astrophysical Journal Letters” .

Small, cool M-dwarf stars like TOI 700 are common in the universe, and in recent years many have been found to host exoplanets, such as the TRAPPIST-1 system and its seven exoplanets, which the James Webb Space Telescope will observe.

The closest exoplanet to the star is TOI 700 b, which is 90% the size of Earth and completes a fast orbit around the star every 10 Earth days. TOI 700 c, which is 2.5 times larger than our planet, completes an orbit every 16 days. These planets likely have tidal coupling, meaning they always show the same side to the star — much like the way the same face on the Moon always faces Earth.

The two exoplanets in the star’s habitable zone, the dee planets, have longer orbits of 37 days and 28 days, respectively, because they are slightly farther from the star. The newly announced planet e is located between planets c and d.

The TESS mission, launched in 2018, monitors large swaths of the night sky for 27 days at a time, observing the brightest stars and tracking their changes in brightness. These luminosity variations indicate planets whose orbits move in front of their stars, called transits. The mission began observing the southern sky in 2018 and then turned to the northern sky. In 2020, the mission focused again on the southern sky for additional observations, revealing the fourth planet in the TOI 700 system.

“Had the star been a little closer or the planet a little bigger, we could have detected TOI 700 and in the first year of the TESS mission,” study co-author Ben Hord, a doctoral candidate at the University of Maryland, College of Columbia, said in a statement. Park, and a graduate researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But the signal was so weak that we needed another year of traffic observations to identify it.”

As researchers use other space and ground-based observatories to follow the intriguing planetary system, more data from the TESS mission continues to be received.

“TESS has just completed its second year of observations of the northern sky,” said Allison Youngblood, research astrophysicist and associate project scientist for the TESS project at the Goddard Space Flight Center. “We can’t wait for the other incredible discoveries hidden in the mission’s data collection.”