Plate No. 6,346 — in order of discoveryEntered 2026-08-20

HIP 81991 b

A cold gas giant world orbiting HIP 81991, a G8 V star, 143 ly from Earth.

Enter the system →Find it in the night sky →

The light now arriving from HIP 81991 set out around 1883.
Its star is within reach of ordinary binoculars (V 6.6).

1 worldtemperate zone1s = 1s

Orbit shapes and relative timing are true — worlds sweep faster near their star, as Kepler demands. Spacing is drawn to true scale when the system allows; wide systems open compressed so inner and outer worlds share the page. Dashed orbits are derived from period alone.

The measures

Earth

1.0 R⊕

HIP 81991 b

12.5 R⊕

Jupiter

11.2 R⊕

frozenEarth 255 K · b 163 Kstar-hot

Life outlook

Hostile

6/ 100

Warmth: 6 · weight 40%
Size: 0 · weight 30%
Star: 87 · weight 20%
Orbit: unmeasured · weight 10%

A strict Earth-similarity index, not a detection: every factor peaks at Earth's own value and they multiply, so one hostile factor sinks the score — only a true Earth twin would reach 100. Equilibrium temperature ignores atmospheres, which can warm a cold world into comfort, or turn a Venus into a furnace.

The world

Class: Gas Giant
Radius: 12.5 R⊕
Mass: 3,019 M⊕
Density: 8.49 g/cm³
Equilibrium temperature: 163 K
Starlight received: 0.12× Earth

The orbit

Period: 5,860 days
Semi-major axis: 6.4 AU
Eccentricity: —

The star

Host: HIP 81991
Spectral type: G8 V
Temperature: 5,100 K
Radius: 2.82 R☉
Mass: 1.09 M☉

The system

Distance: 143 ly · 43.9 pc
Known planets: 1
Stars: 2
Coordinates: RA 251.25° · Dec 6.09°

The observation

Star brightness: V 6.6 · binoculars
Atmospheric spectra: none yet
Stellar age: —

The record

Method: Radial Velocity
Facility: Multiple Facilities
Discovery: 2026
Parameters published: —