Proxima Centauri b
| Exoplanet | List of exoplanets | |
|---|---|---|
 |
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| Parent star | ||
| Star | Proxima Centauri | |
| Constellation | Centaurus | |
| Right ascension | (α) | 14h 29m 42.94853s |
| Declination | (δ) | −62° 40′ 46.1631″ |
| Apparent magnitude | (mV) | 11.13 |
| Distance | 4.224 ly (1.295 pc) |
|
| Spectral type | M6Ve | |
| Mass | (m) | 0.123 (± 0.006) M☉ |
| Radius | (r) | 0.141 (± 0.007) R☉ |
| Temperature | (T) | 3042 (± 117) K |
| Metallicity | [Fe/H] | 0.21 |
| Age | 4.85 Gyr | |
| Physical characteristics | ||
| Minimum mass | (m sin i) |
1.27+0.19 −0.17M⊕ |
| Radius | (r) | ≥1.1 (± 0.3)R⊕ |
| Stellar flux | (F⊙) | 0.65⊕ |
| Temperature | (T) | 234 K (−39 °C; −38 °F) |
| Orbital elements | ||
| Semi-major axis | (a) |
0.0485+0.0041 −0.0051AU |
| Eccentricity | (e) | <0.35 |
| Orbital period | (P) |
11.186+0.001 −0.002d |
| Argument of periastron |
(ω) | 310 (± 50)° |
| Semi-amplitude | (K) | 1.38 (± 0.21)m/s |
| Discovery information | ||
| Discovery date | 24 August 2016 | |
| Discoverer(s) | Anglada-Escudé () et al. | |
| Discovery method | Doppler spectroscopy | |
| Discovery site | European Southern Observatory | |
| Discovery status | Confirmed | |
| Other designations | ||
|
Alpha Centauri Cb, Proxima b, GL 551 b, HIP 70890 b
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| Database references | ||
| Extrasolar Planets Encyclopaedia |
data | |
| SIMBAD | data | |
| Exoplanet Archive | data | |
| Open Exoplanet Catalogue | data | |
Proxima Centauri b (also called Proxima b) is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri, the closest star to the Sun. It is located about 4.2 light-years (1.3 parsecs, 40 trillion km, or 25 trillion miles) from Earth in the constellation of Centaurus, making it the closest known exoplanet to the Solar System. It is unlikely to be habitable, as the planet is subject to stellar wind pressures of more than 2,000 times those experienced by Earth from the solar wind. More information about the planet's physical characteristics is needed for a proper evaluation.
In August 2016, the European Southern Observatory announced the discovery of the planet. The planet was found using the radial velocity method, where periodic Doppler shifts of spectral lines of the host star suggest an orbiting object. From these readings, the radial velocity of the parent star relative to the Earth is varying with an amplitude of about 2 metres (7 feet) per second.
Researchers think that its proximity to Earth offers an opportunity for robotic exploration of the planet with the Starshot project or, at least, "in the coming centuries".
The apparent inclination of Proxima Centauri b's orbit has not yet been measured. The minimum mass of Proxima b is 1.27 M⊕, which would be the actual mass if its orbit were seen edge on from the Earth, producing the maximum Doppler shift. Once its orbital inclination is known, the mass will be calculable. More tilted orientations imply a higher mass, with 90% of possible orientations implying a mass below 3 M⊕. The planet's exact radius is unknown. If it has a rocky composition and a density equal to that of the Earth, then its radius is at least 1.1 R⊕. It could be larger if it has a lower density than the Earth, or a mass higher than the minimum mass. The planet has an equilibrium temperature of 234 K (−39 °C; −38 °F).
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