Kepler-428 b
Kepler-428 b is a hot Jupiter orbiting the K1 V star Kepler-428 in the constellation Lyra. It lies about 2,238 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-428 b?
Kepler-428 b has a radius of 12.11 times that of Earth, or 1.08 times the radius of Jupiter. Its mass is 404 times that of Earth, giving it a density of 1.02 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-428 b in the Habitable Zone?
Kepler-428 b orbits inside the inner edge of the habitable zone of Kepler-428. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-428: 0.496–1.193 AU (conservative: 0.629–1.131 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-428 b
The equilibrium temperature of Kepler-428 b is about 1,070 K (797 °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.
Orbit and Year Length
A year on Kepler-428 b — one full orbit around Kepler-428 — lasts 3.53 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.043 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.22).
How Was Kepler-428 b Discovered?
Kepler-428 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-428 b?
Kepler-428 b is 2,238.4 light-years (686.3 parsecs) from Earth. Light arriving here tonight left the planet about 2,238 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 39,395,840 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-428 b scores 0.08, ranking #4,712 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-428
Kepler-428
- Spectral type
- K1 V
- Surface temperature
- 5,150 K (Sun: 5,772 K)
- Mass
- 0.87 M☉
- Radius
- 0.80 R☉
- Luminosity
- 0.4074 L☉
- Age
- 5.0 billion years (Sun: 4.6)
Planetary System
Kepler-428 b is the only planet known to orbit Kepler-428 so far.
Kepler-428 b — Complete Data
| Radius | 12.110 Earth radii (1.080 Jupiter radii) |
|---|---|
| Mass | 403.63 Earth masses (1.270 Jupiter masses) |
| Density | 1.02 g/cm³ (Earth: 5.51) |
| Orbital period | 3.53 days |
| Orbital distance | 0.043 AU |
| Eccentricity | 0.220 |
| Equilibrium temperature | 1,070 K (797 °C) |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 2,238.4 light-years (686.3 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-10-03. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-428 b
Is Kepler-428 b habitable?
No — Kepler-428 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-428 b?
Kepler-428 b is about 2,238 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 39,395,840 years to get there.
How big is Kepler-428 b compared to Earth?
Kepler-428 b has 12.11 times the radius of Earth and about 404 times its mass.
How long is a year on Kepler-428 b?
One orbit around Kepler-428 takes 3.5 Earth days — short enough that 104 of its years would fit into one Earth year.
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