Lalande 21185

Star

Lalande 21185 — the brightest red dwarf in the northern sky and, at 8.3 light-years, one of the Sun's closest neighbours. An M2V star about 39% of the Sun's mass, it hosts two confirmed planets found from its radial-velocity wobble: a warm super-Earth close in and a cold, more massive world far out.

Open in 3D viewSee Lalande 21185 in the live, interactive 3D map

Key facts

Mass

7.74 × 10²⁹ kg

0.389 M☉

Radius

256,713 km

37% of the Sun's radius

Surface temperature

3,719 K (3,446 °C)

Luminosity

7.46 × 10²⁴ W

Spectral type

M2V (red dwarf)

Science

Physical

Mass: 7.74 × 10²⁹ kg · 0.389 M☉
Radius: 256,713 km · 37% of the Sun's radius
Density: 10,918 kg/m³ · 11× water; Computed from mass and radius
Spectral type: M2V (red dwarf)

Motion through space

Proper motion: 4.81 arcseconds per year · its drift across our sky; SIMBAD — 2020yCat.1350....0G, 2018MNRAS.475.1960F
Radial velocity: -84.6 km/s · approaching the Sun; SIMBAD — 2020yCat.1350....0G, 2018MNRAS.475.1960F
Speed across our line of sight: 58.1 km/s; Computed from proper motion and parallax
Speed through space, relative to the Sun: 103 km/s; Computed from proper motion, parallax and radial velocity

Rotation

Note: Rotates roughly once every 56 days.

Composition

By mass: A red dwarf about 39% of the Sun's mass and a fiftieth of its luminosity, radiating mostly in the infrared. It is metal-rich and relatively quiet, with only occasional mild flares.

Temperature

Surface: 3,719 K (3,446 °C)

Radiation & temperature

Luminosity: 7.46 × 10²⁴ W · 0.0195 L☉
Surface temperature: 3,719 K (3,446 °C)
Peak wavelength: 779 nm · near-infrared (mostly invisible to the eye); Computed (Wien's law) from the surface temperature

Discovery & history

Discovered: 1801
By: Joseph Jérôme Lalande
Method: Telescope
Name: Named for the French astronomer Joseph Jérôme Lalande and its number in his 1801 catalogue. It is also GJ 411 and HD 95735.

Recorded by Joseph Jérôme Lalande around 1801 in the great French star catalogue Histoire Céleste Française, as entry 21185. Its large proper motion was later noted by Friedrich Argelander. In 2019 and 2021 precise radial-velocity surveys (SOPHIE and others) revealed its two planets.

Images

Where to find it — in Ursa Major, the Great Bear (IAU constellation chart). It is an unresolved point of light; its surface has never been imaged. — IAU / Sky & Telescope, R. Sinnott & R. Fienberg (CC BY 3.0) · Wikimedia Commons

Images from open archives · credit shown per image