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Plate No. 156 — in order of discoveryEntered 2014-08-21

HD 189733 b

A molten gas giant world orbiting HD 189733, a K2 V star, 64.4 ly from Earth.

Enter the system →Find it in the night sky →
0.01 AUHD 189733 b
1 world1s = 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⊕

HD 189733 b

12.67 R⊕

Jupiter

11.2 R⊕

frozenEarth 255 K · b 1,209 Kstar-hot

Life outlook

Hostile

2/ 100
Warmth
0 · weight 40%

~1209 K equilibrium vs Earth's 255 K

Size
0 · weight 30%

12.666 R⊕ vs Earth's 1.0 — larger worlds trend gaseous

Star
85 · weight 20%

5052 K vs the Sun's 5772 K

Orbit
100 · weight 10%

e = 0 vs Earth's 0.017 — swings mean climate whiplash

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
12.666 R⊕
Mass
359.148 M⊕
Density
0.94 g/cm³
Equilibrium temperature
1,209 K
Starlight received
356× Earth

The orbit

Period
2.219 days
Semi-major axis
0.0313 AU
Eccentricity
0

The star

Host
HD 189733
Spectral type
K2 V
Temperature
5,052 K
Radius
0.75 R☉
Mass
0.79 M☉

The system

Distance
64.4 ly · 19.8 pc
Known planets
1
Stars
2
Coordinates
RA 300.18° · Dec 22.71°

The observation

Star brightness
V 7.7 · binoculars
Atmospheric spectra
33 transmission · 31 emission
Stellar age
1.4 Gyr

The record

Method
Radial Velocity
Facility
Haute-Provence Observatory
Discovery
2005
Parameters published
—
Discovery paperBouchy et al. 2005