Kepler-28 b
Kepler-28 b is a mini-Neptune orbiting Kepler-28 in the constellation Cygnus. It lies about 1,430 light-years from Earth and was discovered in 2011 using the transit method.
How Big Is Kepler-28 b?
Kepler-28 b has a radius of 1.96 times that of Earth. Its mass is 1.6 times that of Earth, giving it a density of 1.19 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-28 b in the Habitable Zone?
The position of Kepler-28 b relative to the habitable zone of Kepler-28 cannot be precisely determined from the available orbital data.
Habitable zone of Kepler-28: 0.322–0.796 AU (conservative: 0.408–0.754 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-28 b — one full orbit around Kepler-28 — lasts 5.91 Earth days, shorter than Mercury's 88-day year.
How Was Kepler-28 b Discovered?
Kepler-28 b was discovered in 2011 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-28 b?
Kepler-28 b is 1,429.7 light-years (438.4 parsecs) from Earth. Light arriving here tonight left the planet about 1,430 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 25,162,720 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-28 b scores 0.21, ranking #3,737 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-28
Kepler-28
- Surface temperature
- 4,499 K (Sun: 5,772 K)
- Mass
- 0.68 M☉
- Radius
- 0.66 R☉
The Kepler-28 Planetary System
Kepler-28 b is one of 2 known planets in the Kepler-28 system. Its siblings:
- Kepler-28 c (Mini Neptune)
Kepler-28 b — Complete Data
| Radius | 1.959 Earth radii (0.175 Jupiter radii) |
|---|---|
| Mass | 1.63 Earth masses (0.005 Jupiter masses) |
| Density | 1.19 g/cm³ (Earth: 5.51) |
| Orbital period | 5.91 days |
| Earth Similarity Index | 0.21 |
| Distance from Earth | 1,429.7 light-years (438.4 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2011 |
Data: NASA Exoplanet Archive, last updated 2024-06-10. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-28 b
Is Kepler-28 b habitable?
Kepler-28 b is not known to orbit within the habitable zone of Kepler-28, and as a mini-Neptune it is an unlikely candidate for life as we know it.
How far away is Kepler-28 b?
Kepler-28 b is about 1,430 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 25,162,720 years to get there.
How big is Kepler-28 b compared to Earth?
Kepler-28 b has 1.96 times the radius of Earth and about 1.6 times its mass.
How long is a year on Kepler-28 b?
One orbit around Kepler-28 takes 5.9 Earth days — short enough that 62 of its years would fit into one Earth year.
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