TOI700: second Earth-like planet

A second Earth-like planet, named TOI700, has been discovered and it is also in the habitable zone of the M TOI700 star's system.
In this illustration, the newly discovered Earth-like planet, TOI700, within the habitable zone of its star. Credit: NASA

A NASA mission has identified a second planet, named TOI700, Earth-like planet and in orbit around a star that is located about 100 light-years away from us. The planet is likely rocky and is about 95% the size of Earth. The celestial body is the fourth planet to be detected in orbit around the small and cool M TOI700 star. All four were found by NASA’s Transiting Exoplanet Survey Satellite (TESS).

Star M TOI700

Another planet in this system was discovered in 2020, TOI700 d. It is also the size of Earth and both are in the habitable zone of their star. Therefore, they are at the right distance to potentially have liquid water on their surfaces. This possibility suggests that the two planets could potentially be, or have been, inhabited by forms of life. The discovery of the fourth planet was announcedon Tuesday, January 10th, at the 241st meeting of the American Astronomical Society in Seattle.

The study of the exoplanet was published in The Astrophysical Journal Letters. “This is one of the few systems we know of with multiple, small, and habitable planets” said lead study author Emily Gilbert. “This planetary system is an exciting prospect. The TOI700 Earth-like planet is about 10% smaller than TOI700 d. The system shows how further observations by TESS help us to find ever-smaller worlds.” Small and cool M-type stars like M TOI700 are common in the universe and in recent years it has been discovered that many host exoplanets. Another very important system is TRAPPIST-1 and its seven exoplanets that the James Webb Space Telescope will soon observe in detail.

TESS data

The closest to the star is TOI700 b, which is 90% the size of Earth and completes a rapid orbit around the star every 10 Earth days. Then there is TOI700 c, which is 2.5 times larger than our planet and completes an orbit around the star every 16 days. Both of these planets are probably both tide-locked. In other words, they always show the same side to the star, just like the Moon does the same with Earth. The newly announced planet is located in between planets c and d.

“If the planet had been closer to the star or larger, we would have been able to identify TOI700 e in the first year of TESS data” said co-author of the study Ben Hord in a statement. “But the signal was so weak that we needed the additional year of transit observations to identify it.” While researchers use other space and ground-based observatories to conduct observations of the planetary system, more TESS data is coming in. “TESS has just completed its second year of northern sky observations,” said Allison Youngblood, research astrophysicist and TESS Deputy Science lead. “We’re excited to analyze the other data from the TESS mission.”

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