TESS finds its First Earth-sized Exoplanet in the Habitable Zone of a Star

NASA’s Transiting Exoplanet Survey Satellite (TESS) has found its very first Earth-sized planet in the habitable zone of its host star. The discovery was confirmed with the Spitzer Space Telescope. The planet is one of the only few Earth-sized worlds found in a habitable zone. The planet is called TOI 700d and it is about a 100 light years away from the Earth. It orbits TOI 700, an M dwarf (red dwarf) star in the Dorado constellation. It is a key discovery for TESS since it was designed to look for Earth-sized planets in our solar system.

According to the Astronomical Naming Conventions, TOI 700d is the fourth planet from its star. The letters ‘b’ and ‘c’are the other planets closer to the star and the letter ‘a’ is reserved for the star and any companions it might have.

TESS finds planets by analysing large areas of the sky for 27 days at a time. TESS functions by detecting drops in starlight whenever an Exoplanet passes between the Earth and the star. Every time a planet passes in front of its star, it is called a transit. TESS has caught the three planets in the TOI 700 system transiting multiple times.

“TESS was designed and launched specifically to find Earth-sized planets orbiting nearby stars,” said Paul Hertz, astrophysics division director at NASA Headquarters in Washington. “Planets around nearby stars are easiest to follow-up with larger telescopes in space and on Earth. Discovering TOI 700 d is a key science finding for TESS. Confirming the planet’s size and habitable zone status with Spitzer is another win for Spitzer as it approaches the end of science operations this January.”