Kepler-539 b
Kepler-539 b is a cold gas giant orbiting the G2 V star Kepler-539 in the constellation Cygnus. It lies about 1,002 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is Kepler-539 b?
Kepler-539 b has a radius of 8.37 times that of Earth, or 0.75 times the radius of Jupiter. Its mass is 308 times that of Earth, giving it a density of 2.90 g/cm³ — between that of rocky and gaseous planets.
Is Kepler-539 b in the Habitable Zone?
Kepler-539 b orbits inside the inner edge of the habitable zone of Kepler-539. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-539: 0.723–1.702 AU (conservative: 0.916–1.613 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-539 b
The equilibrium temperature of Kepler-539 b is about 388 K (114 °C) — hotter than anywhere on Earth. 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-539 b — one full orbit around Kepler-539 — lasts 125.6 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.499 AU — comparable to the inner Solar System. Its orbit is highly elliptical (eccentricity 0.39), swinging dramatically closer to and farther from its star.
How Was Kepler-539 b Discovered?
Kepler-539 b was discovered in 2016 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-539 b?
Kepler-539 b is 1,002.3 light-years (307.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1024. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 17,640,480 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-539 b scores 0.31, ranking #1,196 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-539
Kepler-539
- Spectral type
- G2 V
- Surface temperature
- 5,820 K (Sun: 5,772 K)
- Mass
- 1.05 M☉
- Radius
- 0.95 R☉
The Kepler-539 Planetary System
Kepler-539 b is one of 2 known planets in the Kepler-539 system. Its siblings:
- Kepler-539 c (Cold Gas Giant)
Kepler-539 b — Complete Data
| Radius | 8.373 Earth radii (0.747 Jupiter radii) |
|---|---|
| Mass | 308.30 Earth masses (0.970 Jupiter masses) |
| Density | 2.90 g/cm³ (Earth: 5.51) |
| Orbital period | 125.63 days |
| Orbital distance | 0.499 AU |
| Eccentricity | 0.390 |
| Equilibrium temperature | 388 K (114 °C) |
| Earth Similarity Index | 0.31 |
| Distance from Earth | 1,002.3 light-years (307.3 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-05-06. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-539 b
Is Kepler-539 b habitable?
No — Kepler-539 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-539 b?
Kepler-539 b is about 1,002 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 17,640,480 years to get there.
How big is Kepler-539 b compared to Earth?
Kepler-539 b has 8.37 times the radius of Earth and about 308 times its mass.
How long is a year on Kepler-539 b?
One orbit around Kepler-539 takes 125.6 Earth days.
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