HD 202772 A b
HD 202772 A b is a hot Jupiter orbiting HD 202772 A in the constellation Capricornus. It lies about 527 light-years from Earth and was discovered in 2019 using the transit method.
How Big Is HD 202772 A b?
HD 202772 A b has a radius of 18.24 times that of Earth, or 1.63 times the radius of Jupiter. Its mass is 324 times that of Earth, giving it a density of 0.29 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HD 202772 A b in the Habitable Zone?
HD 202772 A b orbits inside the inner edge of the habitable zone of HD 202772 A. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 202772 A: 2.305–5.355 AU (conservative: 2.919–5.077 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 202772 A b
The equilibrium temperature of HD 202772 A b is about 2,181 K (1,908 °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. It receives 3,770 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HD 202772 A b — one full orbit around HD 202772 A — lasts 3.31 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.052 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.030).
How Was HD 202772 A b Discovered?
HD 202772 A b was discovered in 2019 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
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 HD 202772 A b?
HD 202772 A b is 526.7 light-years (161.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1500. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 9,269,920 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. HD 202772 A b scores 0.05, ranking #5,248 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 202772 A
HD 202772 A b belongs to a system of 2 stars; it orbits HD 202772 A.
HD 202772 A
- Surface temperature
- 6,442 K (Sun: 5,772 K)
- Mass
- 1.72 M☉
- Radius
- 2.55 R☉
- Luminosity
- 10.2200 L☉
- Age
- 1.6 billion years (Sun: 4.6)
Planetary System
HD 202772 A b is the only planet known to orbit HD 202772 A so far.
HD 202772 A b — Complete Data
| Radius | 18.237 Earth radii (1.627 Jupiter radii) |
|---|---|
| Mass | 323.55 Earth masses (1.018 Jupiter masses) |
| Density | 0.29 g/cm³ (Earth: 5.51) |
| Orbital period | 3.31 days |
| Orbital distance | 0.052 AU |
| Eccentricity | 0.030 |
| Equilibrium temperature | 2,181 K (1,908 °C) |
| Stellar irradiation | 3,770.00× Earth |
| Earth Similarity Index | 0.05 |
| Distance from Earth | 526.7 light-years (161.5 parsecs) |
| Constellation | Capricornus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2026-04-30. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 202772 A b
Is HD 202772 A b habitable?
No — HD 202772 A b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 202772 A b?
HD 202772 A b is about 527 light-years from Earth in the constellation Capricornus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 9,269,920 years to get there.
How big is HD 202772 A b compared to Earth?
HD 202772 A b has 18.24 times the radius of Earth and about 324 times its mass.
How long is a year on HD 202772 A b?
One orbit around HD 202772 A takes 3.3 Earth days — short enough that 110 of its years would fit into one Earth year.
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