WASP-18 c
The parameters of this planet are disputed or ambiguous in the scientific literature.
WASP-18 c is a hot Jupiter orbiting WASP-18 in the constellation Phoenix. It lies about 403 light-years from Earth and was discovered in 2019 using the transit timing variations method.
Is WASP-18 c in the Habitable Zone?
WASP-18 c orbits inside the inner edge of the habitable zone of WASP-18. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of WASP-18: 1.181–2.744 AU (conservative: 1.496–2.602 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on WASP-18 c — one full orbit around WASP-18 — lasts 2.16 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.035 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.015).
How Was WASP-18 c Discovered?
WASP-18 c was discovered in 2019 using the transit timing variations method, with observations from Transiting Exoplanet Survey Satellite (TESS).
Transit timing variations reveal a planet through its gravitational tug on a sibling planet, which makes that sibling's transits arrive slightly early or late. The pattern of these deviations betrays the hidden planet's mass and orbit.
How Far Away Is WASP-18 c?
WASP-18 c is 402.7 light-years (123.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1624. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 7,087,520 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-18 c scores 0.10, ranking #4,442 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: WASP-18
WASP-18 c belongs to a system of 2 stars; it orbits WASP-18.
WASP-18
- Surface temperature
- 6,432 K (Sun: 5,772 K)
- Mass
- 1.29 M☉
- Radius
- 1.32 R☉
- Luminosity
- 2.6800 L☉
- Age
- 1.6 billion years (Sun: 4.6)
The WASP-18 Planetary System
WASP-18 c is one of 2 known planets in the WASP-18 system. Its siblings:
- WASP-18 b (Hot Jupiter)
WASP-18 c — Complete Data
| Mass | 55.20 Earth masses (0.174 Jupiter masses) |
|---|---|
| Orbital period | 2.16 days |
| Orbital distance | 0.035 AU |
| Eccentricity | 0.015 |
| Earth Similarity Index | 0.10 |
| Distance from Earth | 402.7 light-years (123.5 parsecs) |
| Constellation | Phoenix |
| Discovery method | Transit Timing Variations |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2019-12-02. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About WASP-18 c
Is WASP-18 c habitable?
No — WASP-18 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is WASP-18 c?
WASP-18 c is about 403 light-years from Earth in the constellation Phoenix. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 7,087,520 years to get there.
How long is a year on WASP-18 c?
One orbit around WASP-18 takes 2.2 Earth days — short enough that 169 of its years would fit into one Earth year.
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