Kepler-172 b
Kepler-172 b is a mini-Neptune orbiting Kepler-172 in the constellation Lyra. It lies about 2,703 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-172 b?
Kepler-172 b has a radius of 2.35 times that of Earth.
Is Kepler-172 b in the Habitable Zone?
Kepler-172 b orbits inside the inner edge of the habitable zone of Kepler-172. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-172: 0.756–1.794 AU (conservative: 0.957–1.701 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 Kepler-172 b — one full orbit around Kepler-172 — lasts 2.94 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.040 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-172 b Discovered?
Kepler-172 b was discovered in 2014 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 Kepler-172 b?
Kepler-172 b is 2,702.5 light-years (828.6 parsecs) from Earth. Light arriving here tonight left the planet about 2,703 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 47,564,000 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. Kepler-172 b scores 0.24, ranking #3,313 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-172
Kepler-172
- Surface temperature
- 5,526 K (Sun: 5,772 K)
- Radius
- 1.09 R☉
The Kepler-172 Planetary System
Kepler-172 b is one of 4 known planets in the Kepler-172 system. Its siblings:
- Kepler-172 c (Mini Neptune)
- Kepler-172 d (Mini Neptune)
- Kepler-172 e (Mini Neptune)
Kepler-172 b — Complete Data
| Radius | 2.350 Earth radii (0.210 Jupiter radii) |
|---|---|
| Orbital period | 2.94 days |
| Orbital distance | 0.040 AU |
| Earth Similarity Index | 0.24 |
| Distance from Earth | 2,702.5 light-years (828.6 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-172 b
Is Kepler-172 b habitable?
No — Kepler-172 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-172 b?
Kepler-172 b is about 2,703 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 47,564,000 years to get there.
How big is Kepler-172 b compared to Earth?
Kepler-172 b has 2.35 times the radius of Earth.
How long is a year on Kepler-172 b?
One orbit around Kepler-172 takes 2.9 Earth days — short enough that 124 of its years would fit into one Earth year.
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