A New Earth - Size Planet Discovered by TESS
NASA's Transiting Exoplanet Survey Satellite, better known as TESS, has identified an Earth - size world TOI - 700e, orbiting within its stars habitable zone.
Tidally locked and in the goldilocks zone
TOI - 700 is an M2-type star around 102 light-years away in the southern constellation of Dorado. The mass of M - type stars, more commonly known as "red -dwarfs", is below 40% of the mass of our sun, Sol. Their luminosity is very dim and red in color. These stars have a very long lifetime because they burn their hydrogen slowly. An Earth - like planet would be in a torch orbit. A habitable zone or a goldilocks zone exists around the vast majority of red dwarfs. In 2020, astronomers announced the discovery of three exoplanets orbiting TOI-700.
The innermost planet, TOI-700b, is almost exactly Earth-size, is probably rocky and completes an orbit every 10 days. TOI-700c is a gas giant about 2.6 times the size of Earth and orbits the parent star once every 16 days. The outermost planet, TOI-700d, is 1.1 times the size of Earth, and has an orbital period of 38 days. It lies within its star’s goldilocks zone, receives from the star 86% of the energy that the Sun provides to Earth and has a surface temperature of minus 3 degrees Celsius (26 degrees Fahrenheit). An interesting fact about the afforementioned planets is that they are tidally locked to the star, forcing them to rotate only once per orbit, meaning that one side of the planet is always bathed in daylight.
Dr. Emily Gilbert, an astronomer at NASA’s Jet Propulsion Laboratory said; “This is one of only a few systems with multiple, small, habitable-zone planets that we know of, that makes the TOI-700 system an exciting prospect for additional follow up. The newly-discovered planet, TOI-700e, is about 10% smaller than planet TOI-700d, so the system also shows how additional TESS observations help us find smaller and smaller worlds".
The discovery of TOI - 700e
TOI - 700e, which may also be tidally locked, takes 28 days to orbit its star, placing the planet between TOI-700c and TOI-700d in the so-called optimistic habitable zone.
"If the star was a little closer or the planet a little bigger, we might have been able to spot TOI-700e in the first year of TESS data, but the signal was so faint that we needed the additional year of transit observations to identify it.vFollow-up study of the TOI-700 system with space- and ground-based observatories is ongoing and may yield further insights into this rare system," said Ben Hord, a doctoral candidate at the University of Maryland, College Park and a graduate researcher at NASA’s Goddard Space Flight Center.