Ross 128 b
Planet· orbits Ross 128
Ross 128 b — a temperate planet (minimum mass ~1.4 Earth) on a 9.9-day orbit around a calm red dwarf, with an equilibrium temperature near room temperature (~300 K). Whether it holds an atmosphere or water is unknown — it has never been imaged.
Open in 3D viewSee Ross 128 b in the live, interactive 3D map
Key facts
Minimum mass
8.36 × 10²⁴ kg
1.4 M⊕
Year
9.87 Earth days
Distance from Ross 128
7,420,054 km
Science
Physical
- Minimum mass (m·sin i)
- 8.36 × 10²⁴ kg · 1.4 M⊕
- Radial-velocity detection measures m·sin i; the true mass depends on the unknown orbital inclination.
- Radius
- Not measured
- No transit — the radius is a model estimate for a rocky world of this minimum mass; true size unknown.
Orbital
- Semi-major axis
- 7,420,054 km
- From the NASA Exoplanet Archive (radial-velocity orbit)
- Eccentricity
- 0.116
- From the NASA Exoplanet Archive (radial-velocity orbit)
- Inclination
- 0.00 °
- From the NASA Exoplanet Archive (radial-velocity orbit)
- Orbital period
- 9.9 days
- From the NASA Exoplanet Archive (radial-velocity orbit)
- Perihelion
- 6,559,328 km
- Computed from the orbital elements
- Aphelion
- 8,280,781 km
- Computed from the orbital elements
- Mean orbital velocity
- 54.7 km/s
- Computed from the orbital elements
Composition
- Bulk composition
- Presumed rocky (minimum mass ~1.4 Earth); whether it holds water or an atmosphere is unknown, and it has never been imaged.
- Surface appearance
- Appearance based on ESO/M. Kornmesser's artist's concept. No spacecraft has imaged this world, so its real appearance is unknown — The surface shown is an artistic representation, shown only in Visual mode; Realism shows a plain spectral colour.
Radiation & temperature
- Insolation
- 1.47 S⊕ · 1.47× the sunlight Earth receives
- Computed from Ross 128's luminosity and the orbital distance (inverse-square; Earth's sunlight = 1).
- Equilibrium temperature
- 301 K (28 °C)
- Computed model value (no atmosphere assumed), close to room temperature — not a measured surface temperature; real conditions depend on an unknown atmosphere.
Discovery & history
- Method
- Radial-velocity detection (stellar wobble)
- Name
- Designated 'b' as the first planet found around its star, following the IAU convention of lettering planets in discovery order from 'b'.
Announced in 2017 by ESO's HARPS team as one of the nearest temperate exoplanets. Because its host star flares far less than Proxima Centauri, Ross 128 b is often cited as a comparatively gentle environment — though its true conditions remain unknown.
Images
No official imagery available — this object has never been visited and no officially-licensed depiction exists.