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.
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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 (3446 °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
- Spectral type
- M2V (red dwarf)
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 (3446 °C)
Radiation & temperature
- Luminosity
- 7.46 × 10²⁴ W · 0.0195 L☉
- Surface temperature
- 3,719 K (3446 °C)
- Peak wavelength
- 779 nm · near-infrared (mostly invisible to the eye)
Discovery & history
- Discovered
- January 1, 1801
- By
- Joseph Jérôme Lalande
- 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
Images from open archives · credit shown per image