Ross 128

Star

Ross 128 — a quiet red dwarf (M4V) 11 light-years away in Virgo, and the host of the second-closest known temperate exoplanet after Proxima b. Unusually inactive for its type — it flares rarely — which makes its planet an interesting target. About 17% of the Sun's mass.

Open in 3D viewSee Ross 128 in the live, interactive 3D map

Key facts

Mass

3.34 × 10²⁹ kg

0.168 M☉

Radius

137,053 km

20% of the Sun's radius

Surface temperature

3,192 K (2,919 °C)

Luminosity

1.39 × 10²⁴ W

Spectral type

M4V (red dwarf; variable FI Virginis)

Science

Physical

Mass: 3.34 × 10²⁹ kg · 0.168 M☉
Radius: 137,053 km · 20% of the Sun's radius
Density: 30,987 kg/m³ · 31× water; Computed from mass and radius
Spectral type: M4V (red dwarf; variable FI Virginis)

Motion through space

Proper motion: 1.37 arcseconds per year · its drift across our sky; SIMBAD — 2020yCat.1350....0G, 2018MNRAS.475.1960F
Radial velocity: -30.7 km/s · approaching the Sun; SIMBAD — 2020yCat.1350....0G, 2018MNRAS.475.1960F
Speed across our line of sight: 21.8 km/s; Computed from proper motion and parallax
Speed through space, relative to the Sun: 37.6 km/s; Computed from proper motion, parallax and radial velocity

Rotation

Note: Rotates slowly (~120 days) and is comparatively inactive for a red dwarf.

Composition

By mass: A red dwarf about 17% of the Sun's mass, radiating ~0.4% of its light. Unusually quiet magnetically — it flares only rarely — which is part of why its temperate planet is of such interest.

Temperature

Surface: 3,192 K (2,919 °C)

Radiation & temperature

Luminosity: 1.39 × 10²⁴ W · 0.00362 L☉
Surface temperature: 3,192 K (2,919 °C)
Peak wavelength: 908 nm · near-infrared (mostly invisible to the eye); Computed (Wien's law) from the surface temperature

Discovery & history

Discovered: 1926
By: Frank Elmore Ross
Method: Telescope
Name: Named for the American astronomer Frank Elmore Ross and its catalogue number; its variable-star name is FI Virginis.

Catalogued by Frank Elmore Ross in 1926 (entry 128). In 2017 ESO's HARPS spectrograph revealed a temperate planet, Ross 128 b, orbiting this comparatively calm star.

Images

Where to find it — in Virgo, the Maiden (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