Epsilon Eridani b

Planet· orbits the Sun

Epsilon Eridani b (AEgir) — a gas giant of roughly Jupiter's mass orbiting the young Sun-like star Epsilon Eridani, 10.5 light-years away. It circles at about 3.5 AU on a near-circular 7.3-year orbit, outside the region where the debris disk's dust has been cleared. Its mass is genuinely measured (by astrometry), but it has never been imaged and never transits, so its size, appearance and composition are model-based.

Open in 3D viewSee Epsilon Eridani b in the live, interactive 3D map

Key facts

Mass

1.90 × 10²⁷ kg

1 M♃ (318 M⊕)

Year

7.34 Earth years

2,680 Earth days

Distance from Epsilon Eridani

3.53 AU

Science

Physical

Mass: 1.90 × 10²⁷ kg · 1 M♃ (318 M⊕)
Radius: Not measured

Orbital

Semi-major axis: 3.53 AU
Eccentricity: 0.06
Inclination: 0.00 °
Orbital period: 7.34 years
Perihelion: 3.32 AU
Aphelion: 3.74 AU
Mean orbital velocity: 14.3 km/s

Composition

Bulk composition: A cold gas giant — hydrogen and helium with a deep atmosphere, roughly Jupiter's mass. It has never been imaged, so its true appearance is unknown; the map shows an honest flat spectral colour, not a fabricated cloud pattern.
Cloud appearance: Appearance based on ESO/M. Kornmesser's artist's concept. No spacecraft has imaged this world, so its real appearance is unknown — The banded clouds shown are a representation of its class, shown only in Vision mode; Realism shows a plain spectral colour.

Radiation & temperature

Insolation: 0.0273 S⊕ · 3% of the sunlight Earth receives
Equilibrium temperature: 112 K (-161 °C)

Discovery & history

Discovered: August 1, 2000
By: Artie P. Hatzes et al.
Method: Radial-velocity detection (stellar wobble)
Name: Named AEgir — the Norse sea god, husband of Ran (the star) — in the IAU's 2015 NameExoWorlds campaign. Designated 'b' as the first planet found around Epsilon Eridani.

Announced in 2000 by Artie Hatzes and colleagues from radial-velocity data — one of the first giant planets found around a Sun-like star, though the signal was long debated because the young star is magnetically active and mimics planetary wobbles. Combined Hubble and Gaia astrometry (2023) finally confirmed it and pinned down its true mass (~1 Jupiter) and near-circular orbit.

Images

Artist's concept of Epsilon Eridani b (AEgir), the system's gas giant (foreground), amid the star's dusty belts — not a photograph; its true appearance is unknown — NASA / JPL-Caltech (public domain) · Wikimedia Commons

Images from open archives · credit shown per image