GJ 1061

Planetary system

On August 13, 2019, the Red Dots project announced three planets orbiting GJ 1061, detected via the radial velocity method. Initially only minimum masses were known, but further observations allowed true masses to be determined from gravitational interactions between the planets.

All three are less than twice Earth's mass and likely rocky. GJ 1061 d orbits in the conservative habitable zone, and GJ 1061 c orbits near the inner edge of the habitable zone; as of 2025, they are the third- and fourth-nearest known terrestrial exoplanets in the habitable zone, after Proxima Centauri b and Ross 128 b. The star is non-variable and does not suffer flares, increasing the probability that the planets retain their atmospheres.

GJ 1061 c is about 81% more massive than Earth, receives 35% more stellar flux, and has an equilibrium temperature of 275 K; with an Earth-like atmosphere, its surface temperature would be around 34°C. It orbits every 6.7 days at 0.035 au and is probably tidally locked. GJ 1061 d is about 67% more massive than Earth, receives about 40% less stellar flux, and has an equilibrium temperature of 218 K; with an Earth-like atmosphere, its surface temperature would be around 250 K. It orbits every 13 days and is likely tidally locked, though if its orbit is highly eccentric, that eccentricity could desynchronise its rotation, enabling a day/night cycle. Another solution gives it a slightly shorter period of 12.4 days and a slightly smaller minimum mass.

Did You Know?

• The proper motion of GJ 1061 has been known since 1974, but it was then estimated to be about 25 ly distant.
• The RECONS project accurately determined its distance in 1997, at which time it was the 20th-nearest known star system to the Sun.
• The discovery team noted that many more stars like this are likely to be discovered nearby.