Kepler-40 b
Kepler-40 b is a hot Jupiter orbiting the F5 IV star Kepler-40 in the constellation Cygnus. It lies about 7,518 light-years from Earth and was discovered in 2010 using the transit method.
How Big Is Kepler-40 b?
Kepler-40 b has a radius of 13.11 times that of Earth, or 1.17 times the radius of Jupiter. Its mass is 699 times that of Earth, giving it a density of 1.68 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-40 b in the Habitable Zone?
Kepler-40 b orbits inside the inner edge of the habitable zone of Kepler-40. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-40: 1.942–4.506 AU (conservative: 2.459–4.272 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-40 b
The equilibrium temperature of Kepler-40 b is about 1,620 K (1,347 °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-40 b — one full orbit around Kepler-40 — lasts 6.87 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.080 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-40 b Discovered?
Kepler-40 b was discovered in 2010 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-40 b?
Kepler-40 b is 7,517.9 light-years (2,305.0 parsecs) from Earth. Light arriving here tonight left the planet about 7,518 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 132,315,040 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-40 b scores 0.07, ranking #4,957 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-40
Kepler-40
- Spectral type
- F5 IV
- Surface temperature
- 6,510 K (Sun: 5,772 K)
- Mass
- 1.48 M☉
- Radius
- 2.13 R☉
- Age
- 2.8 billion years (Sun: 4.6)
Planetary System
Kepler-40 b is the only planet known to orbit Kepler-40 so far.
Kepler-40 b — Complete Data
| Radius | 13.110 Earth radii (1.170 Jupiter radii) |
|---|---|
| Mass | 699.20 Earth masses (2.200 Jupiter masses) |
| Density | 1.68 g/cm³ (Earth: 5.51) |
| Orbital period | 6.87 days |
| Orbital distance | 0.080 AU |
| Equilibrium temperature | 1,620 K (1,347 °C) |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 7,517.9 light-years (2,305.0 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2010 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-40 b
Is Kepler-40 b habitable?
No — Kepler-40 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-40 b?
Kepler-40 b is about 7,518 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 132,315,040 years to get there.
How big is Kepler-40 b compared to Earth?
Kepler-40 b has 13.11 times the radius of Earth and about 699 times its mass.
How long is a year on Kepler-40 b?
One orbit around Kepler-40 takes 6.9 Earth days — short enough that 53 of its years would fit into one Earth year.
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