Kepler-423 b
Kepler-423 b is a hot Jupiter orbiting the G4 V star Kepler-423 in the constellation Cygnus. It lies about 2,475 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-423 b?
Kepler-423 b has a radius of 13.36 times that of Earth, or 1.19 times the radius of Jupiter. Its mass is 189 times that of Earth, giving it a density of 0.46 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-423 b in the Habitable Zone?
Kepler-423 b orbits inside the inner edge of the habitable zone of Kepler-423. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-423: 0.669–1.585 AU (conservative: 0.847–1.503 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-423 b
The equilibrium temperature of Kepler-423 b is about 1,605 K (1,332 °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-423 b — one full orbit around Kepler-423 — lasts 2.68 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.036 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.019).
How Was Kepler-423 b Discovered?
Kepler-423 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-423 b?
Kepler-423 b is 2,474.7 light-years (758.8 parsecs) from Earth. Light arriving here tonight left the planet about 2,475 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 43,554,720 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-423 b scores 0.07, ranking #4,973 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-423
Kepler-423
- Spectral type
- G4 V
- Surface temperature
- 5,560 K (Sun: 5,772 K)
- Mass
- 0.85 M☉
- Radius
- 0.95 R☉
- Age
- 11.0 billion years (Sun: 4.6)
Planetary System
Kepler-423 b is the only planet known to orbit Kepler-423 so far.
Kepler-423 b — Complete Data
| Radius | 13.361 Earth radii (1.192 Jupiter radii) |
|---|---|
| Mass | 189.10 Earth masses (0.595 Jupiter masses) |
| Density | 0.46 g/cm³ (Earth: 5.51) |
| Orbital period | 2.68 days |
| Orbital distance | 0.036 AU |
| Eccentricity | 0.019 |
| Equilibrium temperature | 1,605 K (1,332 °C) |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 2,474.7 light-years (758.8 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2015-01-22. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-423 b
Is Kepler-423 b habitable?
No — Kepler-423 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-423 b?
Kepler-423 b is about 2,475 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 43,554,720 years to get there.
How big is Kepler-423 b compared to Earth?
Kepler-423 b has 13.36 times the radius of Earth and about 189 times its mass.
How long is a year on Kepler-423 b?
One orbit around Kepler-423 takes 2.7 Earth days — short enough that 136 of its years would fit into one Earth year.
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