Kepler-128 b
Kepler-128 b is a super-Earth orbiting Kepler-128 in the constellation Lyra. It lies about 1,293 light-years from Earth and was discovered in 2013 using the transit method.
How Big Is Kepler-128 b?
Kepler-128 b has a radius of 1.42 times that of Earth. Its mass is 3.8 times that of Earth, giving it a density of 7.22 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is Kepler-128 b in the Habitable Zone?
The position of Kepler-128 b relative to the habitable zone of Kepler-128 cannot be precisely determined from the available orbital data.
Habitable zone of Kepler-128: 1.351–3.160 AU (conservative: 1.711–2.996 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-128 b — one full orbit around Kepler-128 — lasts 15.0 Earth days, shorter than Mercury's 88-day year.
How Was Kepler-128 b Discovered?
Kepler-128 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 Kepler-128 b?
Kepler-128 b is 1,292.8 light-years (396.4 parsecs) from Earth. Light arriving here tonight left the planet about 1,293 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 22,753,280 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-128 b scores 0.29, ranking #1,957 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-128
Kepler-128
- Surface temperature
- 6,072 K (Sun: 5,772 K)
- Mass
- 1.18 M☉
- Radius
- 1.66 R☉
The Kepler-128 Planetary System
Kepler-128 b is one of 2 known planets in the Kepler-128 system. Its siblings:
- Kepler-128 c (Super Earth)
Kepler-128 b — Complete Data
| Radius | 1.421 Earth radii (0.127 Jupiter radii) |
|---|---|
| Mass | 3.79 Earth masses (0.012 Jupiter masses) |
| Density | 7.22 g/cm³ (Earth: 5.51) |
| Orbital period | 15.00 days |
| Earth Similarity Index | 0.29 |
| Distance from Earth | 1,292.8 light-years (396.4 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2013 |
Data: NASA Exoplanet Archive, last updated 2024-06-10. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-128 b
Is Kepler-128 b habitable?
Kepler-128 b is not known to orbit within the habitable zone of Kepler-128, and as a super-Earth it is an unlikely candidate for life as we know it.
How far away is Kepler-128 b?
Kepler-128 b is about 1,293 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 22,753,280 years to get there.
How big is Kepler-128 b compared to Earth?
Kepler-128 b has 1.42 times the radius of Earth and about 3.8 times its mass.
How long is a year on Kepler-128 b?
One orbit around Kepler-128 takes 15.0 Earth days — short enough that 24 of its years would fit into one Earth year.
Explore Kepler-128 b in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
