16 Cyg B b
16 Cyg B b is a cold gas giant orbiting 16 Cyg B in the constellation Cygnus. It lies about 69 light-years from Earth and was discovered in 1996 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is 16 Cyg B b in the Habitable Zone?
16 Cyg B b orbits inside the conservative habitable zone of 16 Cyg B — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
Habitable zone of 16 Cyg B: 0.841–1.983 AU (conservative: 1.066–1.880 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 16 Cyg B b — one full orbit around 16 Cyg B — lasts 798.5 Earth days, longer than an Earth year. It orbits at an average distance of 1.660 AU. Its orbit is highly elliptical (eccentricity 0.68), swinging dramatically closer to and farther from its star.
How Was 16 Cyg B b Discovered?
16 Cyg B b was discovered in 1996 using the radial velocity method, with observations from Multiple Observatories.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is 16 Cyg B b?
16 Cyg B b is 68.9 light-years (21.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1958. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,212,640 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. 16 Cyg B b scores 0.37, ranking #638 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: 16 Cyg B
16 Cyg B b belongs to a system of 3 stars; it orbits 16 Cyg B.
16 Cyg B
- Surface temperature
- 5,750 K (Sun: 5,772 K)
- Mass
- 1.08 M☉
- Radius
- 1.13 R☉
Planetary System
16 Cyg B b is the only planet known to orbit 16 Cyg B so far.
16 Cyg B b — Complete Data
| Mass (best estimate) | 565.74 Earth masses |
|---|---|
| Orbital period | 798.50 days |
| Orbital distance | 1.660 AU |
| Eccentricity | 0.680 |
| Earth Similarity Index | 0.37 |
| Distance from Earth | 68.9 light-years (21.1 parsecs) |
| Constellation | Cygnus |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 1996 |
Data: NASA Exoplanet Archive, last updated 2018-09-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About 16 Cyg B b
Is 16 Cyg B b habitable?
16 Cyg B b orbits within the habitable zone of 16 Cyg B, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is 16 Cyg B b?
16 Cyg B b is about 69 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,212,640 years to get there.
How long is a year on 16 Cyg B b?
One orbit around 16 Cyg B takes 798.5 Earth days.
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