PH2 b
PH2 b is a cold gas giant orbiting PH2 in the constellation Cygnus. It lies about 1,122 light-years from Earth and was discovered in 2013 using the transit method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
How Big Is PH2 b?
PH2 b has a radius of 9.34 times that of Earth, or 0.83 times the radius of Jupiter. Its mass is 87.1 times that of Earth, giving it a density of 0.58 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is PH2 b in the Habitable Zone?
PH2 b orbits within the optimistic habitable zone of PH2 — the broader region where liquid water might be possible under favorable atmospheric conditions.
Habitable zone of PH2: 0.703–1.659 AU (conservative: 0.891–1.573 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on PH2 b
The equilibrium temperature of PH2 b is about 295 K (22 °C) — in a range broadly comparable to Earth, whose equilibrium temperature is 255 K. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 1.20 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on PH2 b — one full orbit around PH2 — lasts 282.5 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.833 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.22).
How Was PH2 b Discovered?
PH2 b was discovered in 2013 using the transit method, with observations from Kepler.
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 PH2 b?
PH2 b is 1,121.5 light-years (343.9 parsecs) from Earth. Light arriving here tonight left the planet about 1,122 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 19,738,400 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. PH2 b scores 0.41, ranking #424 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: PH2
PH2
- Surface temperature
- 5,734 K (Sun: 5,772 K)
- Mass
- 0.97 M☉
- Radius
- 0.95 R☉
- Luminosity
- 0.8740 L☉
- Age
- 4.1 billion years (Sun: 4.6)
Planetary System
PH2 b is the only planet known to orbit PH2 so far.
PH2 b — Complete Data
| Radius | 9.337 Earth radii (0.833 Jupiter radii) |
|---|---|
| Mass | 87.08 Earth masses (0.274 Jupiter masses) |
| Density | 0.58 g/cm³ (Earth: 5.51) |
| Orbital period | 282.53 days |
| Orbital distance | 0.833 AU |
| Eccentricity | 0.215 |
| Equilibrium temperature | 295 K (22 °C) |
| Stellar irradiation | 1.20× Earth |
| Earth Similarity Index | 0.41 |
| Distance from Earth | 1,121.5 light-years (343.9 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2013 |
Data: NASA Exoplanet Archive, last updated 2024-09-13. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About PH2 b
Is PH2 b habitable?
PH2 b orbits within the habitable zone of PH2, the region where liquid water could exist on a planet's surface. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is PH2 b?
PH2 b is about 1,122 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 19,738,400 years to get there.
How big is PH2 b compared to Earth?
PH2 b has 9.34 times the radius of Earth and about 87.1 times its mass.
How long is a year on PH2 b?
One orbit around PH2 takes 282.5 Earth days.
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