The second potentially habitable Earth-sized planet found orbiting a nearby star

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NASA mission spotted An Earth-sized exoplanet orbiting a small star about 100 light-years away.

The planet, called TOI 700 e, is probably rocky and 95% the size of our world. The celestial body is the fourth planet to be discovered orbiting the small dwarf star M TOI 700. Both outer planets They were found by NASA’s Transiting Exoplanet Survey Satellite, or TESS mission.

Another planet in the system, discovered in 2020 and named TOI 700 d, is also the size of Earth. Each of these exoplanets is in the habitable zone of its star, or the appropriate distance from the star that liquid water is likely to exist on their surfaces. The possibility of liquid water suggests that the planets themselves could be, or may once have been, habitable for life.

The discovery of the fourth planet was announced on Tuesday at the 241st meeting of the Cabinet American Astronomical Society In Seattle, a study on an exoplanet has been accepted for publication by the Astrophysical Journal Letters.

“This is one of only a few systems with multiple, minor planets and habitable zones that we know of,” Emily Gilbert, lead study author and postdoctoral fellow at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement.

“This makes the TOI 700 system an exciting opportunity for additional follow-up. Planet e is about 10% smaller than Planet d, so the system also shows how additional TESS observations help us find smaller and smaller worlds.”

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

Closest to the star is TOI 700 b, which is 90% of Earth’s size and completes one fast orbit around the star every 10 Earth days. Then there is TOI 700 c, which is 2.5 times more massive than our planet and finishes one orbit around the star every 16 days. These planets are probably pheno-locked, which means they always show the same side to the star — much like how the same side of the Moon always faces Earth.

The exoplanets in the star’s habitable zone, planets d and e, 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 parts of the night sky for 27 days at a time, staring at the brightest stars and tracking their changes in brightness. These dips in luminosity indicate the presence of orbiting planets as they pass in front of their stars, and are called transits. The mission began observing the southern sky in 2018, and then switched to the northern sky. In 2020, the mission refocused on the southern sky again for additional observations, revealing the fourth planet in the TOI 700 system.

said study co-author Ben Hurd, PhD student at the University of Maryland, College Park, and alumnus Researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement. “But the signal was so weak that we needed an extra year of observing the transit to determine it.”

As researchers use other space and ground-based observatories to make follow-up observations of the intriguing planetary system, more TESS data is pouring in.

“TESS has completed its second year of observing the northern sky,” said Alison Youngblood, astrophysicist and TESS deputy project scientist at Goddard. “We look forward to other exciting discoveries hidden in the mission’s data trove.”