Kepler-666 b
Kepler-666 b is a mini-Neptune orbiting Kepler-666 in the constellation Cygnus. It lies about 4,921 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is Kepler-666 b?
Kepler-666 b has a radius of 2.40 times that of Earth.
Is Kepler-666 b in the Habitable Zone?
The position of Kepler-666 b relative to the habitable zone of Kepler-666 cannot be precisely determined from the available orbital data.
Habitable zone of Kepler-666: 0.813–1.909 AU (conservative: 1.029–1.810 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-666 b — one full orbit around Kepler-666 — lasts 4.50 Earth days, shorter than Mercury's 88-day year.
How Was Kepler-666 b Discovered?
Kepler-666 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-666 b?
Kepler-666 b is 4,920.7 light-years (1,508.7 parsecs) from Earth. Light arriving here tonight left the planet about 4,921 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 86,604,320 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-666 b scores 0.24, ranking #3,363 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-666
Kepler-666
- Surface temperature
- 5,887 K (Sun: 5,772 K)
- Mass
- 1.03 M☉
- Radius
- 1.05 R☉
- Age
- 3.8 billion years (Sun: 4.6)
Planetary System
Kepler-666 b is the only planet known to orbit Kepler-666 so far.
Kepler-666 b — Complete Data
| Radius | 2.400 Earth radii (0.214 Jupiter radii) |
|---|---|
| Orbital period | 4.50 days |
| Earth Similarity Index | 0.24 |
| Distance from Earth | 4,920.7 light-years (1,508.7 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-666 b
Is Kepler-666 b habitable?
Kepler-666 b is not known to orbit within the habitable zone of Kepler-666, and as a mini-Neptune it is an unlikely candidate for life as we know it.
How far away is Kepler-666 b?
Kepler-666 b is about 4,921 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 86,604,320 years to get there.
How big is Kepler-666 b compared to Earth?
Kepler-666 b has 2.40 times the radius of Earth.
How long is a year on Kepler-666 b?
One orbit around Kepler-666 takes 4.5 Earth days — short enough that 81 of its years would fit into one Earth year.
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