Nasa discovers Earth-sized planet that may have water orbiting habitable zone of TOI 700 star
Nasa’s Transiting Exoplanet Survey Satellite (Tess) recently discovered an Earth-sized world that may have liquid water in it orbiting around a star.
The planet called TOI 700 e is 95% of the Earth’s size and possibly rocky.
This is the fourth planet to be discovered in this system. The previous three were TOI 700 b, c and d.
TOI 700 is the star the planets orbit around, though e and d are the only ones that orbit the habitable zone.
The habitable zone, which is also known as the “Goldilocks zone”, is an area that is just far away enough from the star where water can exist on a planet’s surface and the conditions are neither too hot nor too cold for life to survive.
Nasa said its scientists need another year of Tess observations to discover TOI 700 e.
“This is one of only a few systems with multiple, small, habitable-zone planets that we know of,” said Emily Gilbert, a postdoctoral fellow at Nasa’s Jet Propulsion Laboratory in Southern California who led the study. “That makes the TOI 700 system an exciting prospect 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.”
TOI 700 is a small, cool M dwarf star located around 100 light-years away in the southern constellation Dorado, and the TOI 700 e takes 28 days to orbit around it. Planet TOI 700 d, which was discovered in 2020, is in a 37-day orbit.
The innermost planet, TOI 700 b, is about 90% Earth’s size and orbits the star every 10 days. TOI 700 c is over 2.5 times bigger than Earth and completes an orbit every 16 days. The planets are probably tidally locked, which means they spin only once per orbit, which means one side is always facing the star.
Tess monitors large swaths of the sky, called sectors, for approximately 27 days at a time, which allows the satellite to track changes in stellar brightness caused by a planet crossing in front of its star from our perspective. The mission used this strategy to observe the southern sky in 2018 before turning to observe the northern sky.
In 2020, it returned to the southern sky for additional observation.
The extra data allowed the team to refine the original planet sizes, which are about 10% smaller than initially calculated.
Finding systems with Earth-size worlds helps scientists learn more about the history of our own solar system.
A follow-up study of the TOI 700 system with space- and ground-based observatories is ongoing, Gilbert said, and may yield further insights.