Gliese 581

Star

Gliese 581 - a red dwarf 20.5 light-years away in Libra that became one of the most famous exoplanet hosts of the 2000s. It has three confirmed planets; two further 'habitable' worlds announced in 2009-2010 (581 d and g) were later shown to be illusions of the star's own activity - a landmark cautionary tale.

Open in 3D viewSee Gliese 581 in the live, interactive 3D map

Key facts

Mass

5.87 × 10²⁹ kg

0.295 M☉

Radius

210,101 km

30% of the Sun's radius

Surface temperature

3,500 K (3,227 °C)

Luminosity

4.75 × 10²⁴ W

Spectral type

M3V (red dwarf)

Science

Physical

Mass: 5.87 × 10²⁹ kg · 0.295 M☉
Radius: 210,101 km · 30% of the Sun's radius
Density: 15,103 kg/m³ · 15× water; Computed from mass and radius
Spectral type: M3V (red dwarf)

Motion through space

Proper motion: 1.23 arcseconds per year · its drift across our sky; SIMBAD — 2020yCat.1350....0G, 2018MNRAS.475.1960F
Radial velocity: -9.2 km/s · approaching the Sun; SIMBAD — 2020yCat.1350....0G, 2018MNRAS.475.1960F
Speed across our line of sight: 36.6 km/s; Computed from proper motion and parallax
Speed through space, relative to the Sun: 37.7 km/s; Computed from proper motion, parallax and radial velocity

Composition

By mass: A red dwarf about 30% of the Sun's mass and ~1% of its light; relatively quiet, which made its planets detectable.

Temperature

Surface: 3,500 K (3,227 °C)

Radiation & temperature

Luminosity: 4.75 × 10²⁴ W · 0.0124 L☉
Surface temperature: 3,500 K (3,227 °C)
Peak wavelength: 828 nm · near-infrared (mostly invisible to the eye); Computed (Wien's law) from the surface temperature

Discovery & history

Method: Telescope
Name: A catalogue designation (Gliese 581); the star also carries the variable-star name HO Librae.

From 2005 ESO's HARPS spectrograph found a growing family of planets here. The 2010 claim of a habitable planet '581 g' made headlines worldwide, but further analysis showed 581 d and g were artefacts of stellar activity, not planets - a turning point in how the field treats marginal signals.

Images

Where to find it — in Libra, the Scales (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