HD 20329 b
HD 20329 b is a lava world orbiting HD 20329 in the constellation Aries. It lies about 208 light-years from Earth and was discovered in 2022 using the transit method.
How Big Is HD 20329 b?
HD 20329 b has a radius of 1.72 times that of Earth. Its mass is 7.4 times that of Earth, giving it a density of 8.06 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is HD 20329 b in the Habitable Zone?
HD 20329 b orbits inside the inner edge of the habitable zone of HD 20329. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 20329: 0.803–1.901 AU (conservative: 1.017–1.803 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 20329 b
The equilibrium temperature of HD 20329 b is about 2,141 K (1,868 °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 3,474 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HD 20329 b — one full orbit around HD 20329 — lasts just 22.2 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.018 AU — closer to its star than Mercury is to the Sun.
How Was HD 20329 b Discovered?
HD 20329 b was discovered in 2022 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 20329 b?
HD 20329 b is 207.7 light-years (63.7 parsecs) from Earth. Light arriving here tonight left the planet around the year 1819. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,655,520 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. HD 20329 b scores 0.27, ranking #2,640 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 20329
HD 20329
- Surface temperature
- 5,596 K (Sun: 5,772 K)
- Mass
- 0.90 M☉
- Radius
- 1.13 R☉
- Luminosity
- 1.1200 L☉
- Age
- 11.0 billion years (Sun: 4.6)
Planetary System
HD 20329 b is the only planet known to orbit HD 20329 so far.
HD 20329 b — Complete Data
| Radius | 1.720 Earth radii (0.153 Jupiter radii) |
|---|---|
| Mass | 7.42 Earth masses (0.023 Jupiter masses) |
| Density | 8.06 g/cm³ (Earth: 5.51) |
| Orbital period | 0.93 days |
| Orbital distance | 0.018 AU |
| Equilibrium temperature | 2,141 K (1,868 °C) |
| Stellar irradiation | 3,474.00× Earth |
| Earth Similarity Index | 0.27 |
| Distance from Earth | 207.7 light-years (63.7 parsecs) |
| Constellation | Aries |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2022 |
Data: NASA Exoplanet Archive, last updated 2022-11-29. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 20329 b
Is HD 20329 b habitable?
No — HD 20329 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 20329 b?
HD 20329 b is about 208 light-years from Earth in the constellation Aries. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,655,520 years to get there.
How big is HD 20329 b compared to Earth?
HD 20329 b has 1.72 times the radius of Earth and about 7.4 times its mass.
How long is a year on HD 20329 b?
One orbit around HD 20329 takes 0.9 Earth days — short enough that 394 of its years would fit into one Earth year.
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