WASP-123 b
WASP-123 b is a hot Jupiter orbiting the G5 star WASP-123 in the constellation Sagittarius. It lies about 646 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is WASP-123 b?
WASP-123 b has a radius of 15.13 times that of Earth, or 1.35 times the radius of Jupiter.
Is WASP-123 b in the Habitable Zone?
The position of WASP-123 b relative to the habitable zone of WASP-123 cannot be precisely determined from the available orbital data.
Temperature on WASP-123 b
The equilibrium temperature of WASP-123 b is about 1,500 K (1,227 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
How Was WASP-123 b Discovered?
WASP-123 b was discovered in 2016 using the transit method, with observations from SuperWASP.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is WASP-123 b?
WASP-123 b is 645.8 light-years (198.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1381. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 11,366,080 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. WASP-123 b scores 0.06, ranking #5,110 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: WASP-123
WASP-123 b belongs to a system of 2 stars; it orbits WASP-123.
WASP-123
- Spectral type
- G5
Planetary System
WASP-123 b is the only planet known to orbit WASP-123 so far.
WASP-123 b — Complete Data
| Radius | 15.132 Earth radii (1.350 Jupiter radii) |
|---|---|
| Density | 0.49 g/cm³ (Earth: 5.51) |
| Equilibrium temperature | 1,500 K (1,227 °C) |
| Earth Similarity Index | 0.06 |
| Distance from Earth | 645.8 light-years (198.0 parsecs) |
| Constellation | Sagittarius |
| Discovery method | Transit |
| Discovery facility | SuperWASP |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2025-12-18. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About WASP-123 b
Is WASP-123 b habitable?
WASP-123 b is not known to orbit within the habitable zone of WASP-123, and as a hot Jupiter it is an unlikely candidate for life as we know it.
How far away is WASP-123 b?
WASP-123 b is about 646 light-years from Earth in the constellation Sagittarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 11,366,080 years to get there.
How big is WASP-123 b compared to Earth?
WASP-123 b has 15.13 times the radius of Earth.
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