The first roughly Earth-size planet that NASA's TESS satellite found in a star's habitable zone was TOI-700 d, announced in 2020 by a team led by Emily Gilbert. TESS spots planets by the small dip in starlight as they cross the face of their star. TOI-700 d is about 1.15 times Earth's width. It circles a red dwarf about 101 light-years away once every 37 days.
It shares its star with three other known planets. TOI-700 c is a puffy sub-Neptune. TOI-700 e, found in 2023 after an extra year of TESS data, is about 95 percent of Earth's size and also orbits in the habitable zone. Planet d sits in the conservative habitable zone, where liquid water could last for most of a planet's life, and gets about 86 percent of the light Earth receives from the Sun. It is probably tidally locked, with one side always facing its star. The discovery team also noted the star is relatively quiet, which matters because strong flares can strip a planet's air.
Whether it has an atmosphere is unknown. A team led by Gabrielle Suissa ran 20 three-dimensional climate simulations. They found the signals any atmosphere would leave are below 10 parts per million, likely too faint for the James Webb Space Telescope. Its mass has also been uncertain. In a June 2025 conference abstract, the discovery team reported a first measured mass of about 2.4 Earth masses, from the ESPRESSO spectrograph, implying a rocky world. The 1.58 Earth masses shown on this page is the archive's figure.
TerraForge's model classifies TOI-700 d as earth-like at about 273 K. On size, orbit and starlight, the science agrees that it is a likely rocky planet receiving a little less light than Earth. What the model cannot know is whether it has the air and water that would make that label true.