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Planet profiles

TOI-1266 d

Water-Rich · 117 light-years away · Last reviewed October 14, 2026

TOI-1266 d rendered in TerraForge from its measured mass, orbit and star
TerraForge's rendering of TOI-1266 d, generated by our physics engine from its measured mass, size, orbit and star. An illustration of what the science suggests, not a photograph.
TerraForge classification
Water-Rich
Host star
TOI-1266 (M2)
Distance
117 light-years
Orbit
32.5 days
Mass
3.68 × Earth
Radius
1.74 × Earth
Discovered
2025, transit timing variations

Figures from the NASA Exoplanet Archive. The classification is TerraForge’s, from its physics model.

TOI-1266 d is the third planet of TOI-1266, a red dwarf about 117 light-years away, and the only one of the three that does not cross in front of the star. It orbits every 32.5 days and has a mass of about 3.7 Earth masses. It was found largely through its effect on the other two planets.

TOI-1266 b and c were discovered by NASA's TESS satellite in 2020 and are unusual: the larger planet, b, orbits inside the smaller one, c, which researchers call an inverted arrangement. In 2023 a team led by Ryan Cloutier measured the planets' masses with the HARPS-N spectrograph and found a third signal at about 32 days, which they listed as a candidate. In 2024 a team led by Michael Greklek-McKeon measured how the transits of b and c arrive slightly early or late, because of the planets' gravitational tugs on one another. Combining those timing shifts with the earlier measurements, they confirmed TOI-1266 d.

The confirmed system has an odd layout: b and d are close to a 3 to 1 ratio of orbital periods, with c between them out of step. Greklek-McKeon's team found that b and d travel on slightly oval orbits, which may heat b's interior and puff up its atmosphere. According to the NASA Exoplanet Archive, TOI-1266 d receives about 1.3 times the light Earth gets from the Sun, with an estimated equilibrium temperature of about 290 kelvin. Since it does not transit, its size is unknown; the archive's radius is an estimate. Its siblings have low densities that suggest thick gas envelopes, according to a 2024 study led by Dakotah Tyler.

Sources

  1. Tidally Heated Sub-Neptunes, Refined Planetary Compositions, and Confirmation of a Third Planet in the TOI-1266 System — arXiv (The Astronomical Journal)
  2. Masses, Revised Radii, and a Third Planet Candidate in the "Inverted" Planetary System Around TOI-1266 — arXiv (Monthly Notices of the Royal Astronomical Society)
  3. Revised Masses for Low Density Planets Orbiting the Disordered M-dwarf System TOI-1266 — arXiv (The Astrophysical Journal)
A banded gas giant with four moons in different colors: a yellow sulfur moon, two rust-red rock moons and a blue water moon

New: Choose What Your Moons Are Made Of 🌙

Every moon used to be grey rock, white ice or blue ocean, decided for you. Now each one has a "Made of" choice in the builder's Moons tab — silicate rock, iron, water ice, carbon, sulfur, or nitrogen and methane ice — and the physics decides what that becomes. Put water ice too close to the star and it boils off to bare rock. Put sulfur where a neighbouring moon keeps it tidally flexed and it erupts in Io's yellows. Give a Titan-sized moon nitrogen ice far from the sun and it wraps itself in haze. Hang a water moon about the mass of Earth off a giant planet in the habitable zone and it can hold air and open seas — scored for life on the same scale as a planet, with a day as long as its orbit. A tint slider nudges the colour, but only as far as that material could really go.

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