LHS 1140

Star

LHS 1140 - a small, unusually quiet red dwarf 48.9 light-years away in Cetus, host to two TRANSITING rocky planets. The outer one, LHS 1140 b, is a temperate super-Earth in the star's habitable zone - dense, rocky, and one of the most promising nearby worlds for the search for water and atmospheres.

Open in 3D viewSee LHS 1140 in the live, interactive 3D map

Key facts

Mass

3.66 × 10²⁹ kg

0.184 M☉

Radius

150,271 km

22% of the Sun's radius

Surface temperature

3,096 K (2,823 °C)

Luminosity

1.45 × 10²⁴ W

Spectral type

M4.5V (red dwarf)

Science

Physical

Mass: 3.66 × 10²⁹ kg · 0.184 M☉
Radius: 150,271 km · 22% of the Sun's radius
Density: 25,747 kg/m³ · 26× water; Computed from mass and radius
Spectral type: M4.5V (red dwarf)

Motion through space

Proper motion: 0.676 arcseconds per year · its drift across our sky; SIMBAD — 2020yCat.1350....0G, 2022ApJ...935..104M
Radial velocity: -13.3 km/s · approaching the Sun; SIMBAD — 2020yCat.1350....0G, 2022ApJ...935..104M
Speed across our line of sight: 48 km/s; Computed from proper motion and parallax
Speed through space, relative to the Sun: 49.8 km/s; Computed from proper motion, parallax and radial velocity

Rotation

Note: Rotates slowly (~130 days) and shows little activity — ideal for sensitive planet studies.

Composition

By mass: A cool red dwarf under a fifth of the Sun's mass and well under 1% of its light. It is old and magnetically calm — unusually quiet for an M dwarf — which is exactly why its transiting planets are such clean targets for the search for atmospheres and water.

Temperature

Surface: 3,096 K (2,823 °C)

Radiation & temperature

Luminosity: 1.45 × 10²⁴ W · 0.0038 L☉
Surface temperature: 3,096 K (2,823 °C)
Peak wavelength: 936 nm · near-infrared (mostly invisible to the eye); Computed (Wien's law) from the surface temperature

Discovery & history

Method: Telescope
Name: A catalogue designation (Luyten Half-Second star 1140); the star has no proper name.

Its planets were found transiting by the MEarth ground survey and confirmed with ESO's HARPS from 2017. Because LHS 1140 is old and magnetically calm, its planets are prime targets: in 2024 JWST began probing planet b for signs of an atmosphere and even a possible ocean.

Images

Where to find it — in Cetus, the Sea Monster (IAU constellation chart). To the eye it is a single point of light; no telescope has imaged its surface. — IAU / Sky & Telescope, R. Sinnott & R. Fienberg (CC BY 3.0) · Wikimedia Commons

Images from open archives · credit shown per image