WASP-173 A b
WASP-173 A b is a hot Jupiter orbiting the G3 star WASP-173 A in the constellation Sculptor. It lies about 760 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is WASP-173 A b?
WASP-173 A b has a radius of 13.45 times that of Earth, or 1.20 times the radius of Jupiter. Its mass is 1,173 times that of Earth, giving it a density of 2.84 g/cm³ — between that of rocky and gaseous planets.
Is WASP-173 A b in the Habitable Zone?
WASP-173 A b orbits inside the inner edge of the habitable zone of WASP-173 A. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of WASP-173 A: 0.838–1.974 AU (conservative: 1.062–1.871 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on WASP-173 A b
The equilibrium temperature of WASP-173 A b is about 1,880 K (1,607 °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.
Orbit and Year Length
A year on WASP-173 A b — one full orbit around WASP-173 A — lasts just 33.3 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.025 AU — closer to its star than Mercury is to the Sun.
How Was WASP-173 A b Discovered?
WASP-173 A b was discovered in 2018 using the transit method, with observations from SuperWASP-South.
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-173 A b?
WASP-173 A b is 759.9 light-years (233.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1267. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 13,374,240 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-173 A b scores 0.07, ranking #4,999 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: WASP-173 A
WASP-173 A b belongs to a system of 2 stars; it orbits WASP-173 A.
WASP-173 A
- Spectral type
- G3
- Surface temperature
- 5,800 K (Sun: 5,772 K)
- Mass
- 1.05 M☉
- Radius
- 1.11 R☉
- Age
- 6.8 billion years (Sun: 4.6)
Planetary System
WASP-173 A b is the only planet known to orbit WASP-173 A so far.
WASP-173 A b — Complete Data
| Radius | 13.451 Earth radii (1.200 Jupiter radii) |
|---|---|
| Mass | 1,172.79 Earth masses (3.690 Jupiter masses) |
| Density | 2.84 g/cm³ (Earth: 5.51) |
| Orbital period | 1.39 days |
| Orbital distance | 0.025 AU |
| Equilibrium temperature | 1,880 K (1,607 °C) |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 759.9 light-years (233.0 parsecs) |
| Constellation | Sculptor |
| Discovery method | Transit |
| Discovery facility | SuperWASP-South |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2018-10-24. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About WASP-173 A b
Is WASP-173 A b habitable?
No — WASP-173 A b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is WASP-173 A b?
WASP-173 A b is about 760 light-years from Earth in the constellation Sculptor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 13,374,240 years to get there.
How big is WASP-173 A b compared to Earth?
WASP-173 A b has 13.45 times the radius of Earth and about 1,173 times its mass.
How long is a year on WASP-173 A b?
One orbit around WASP-173 A takes 1.4 Earth days — short enough that 263 of its years would fit into one Earth year.
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