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. It is the closest known exoplanet to the Solar System and the closest potentially habitable exoplanet known.
In August 2016, the European Southern Observatory announced the discovery of the planet. Shortly after the discovery, researchers investigating the habitable potential of Proxima b suggested that the exoplanet may be the nearest possible location for life beyond our solar system. Researchers think that its proximity to Earth offers an opportunity for robotic exploration of the planet in the future.
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 component of its velocity relative to the Earth is about 5 km/h (3 mph). …
Left: This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Right: Artist’s conception of Proxima Centauri b along with the Alpha Centauri binary system ( upload.wikimedia.org/wikipedia/ … ntauri.jpg ).
… Proxima Centauri b orbits its host star every 11.186 days at a semi-major axis distance of approximately 0.05 astronomical units (7,000,000 km; 5,000,000 mi), which is 5% of 1 AU (thus, Earth is 20 times farther away from its own host star, the Sun). Comparatively, Mercury, the closest planet to the Sun, has a semi-major axis distance of 0.39 AU. Proxima Centauri b receives from its host star about 65% of the amount of solar flux that the Earth receives from the Sun. However, Proxima Centauri b receives about 400 times more X-ray flux than the Earth receives.
The habitability of Proxima Centauri b has not been established. The exoplanet was announced as orbiting within the habitable zone of Proxima Centauri, the region where, with the correct conditions and atmospheric properties, liquid water may exist on the surface of the planet. Its host star is a red dwarf, with about an eighth of the mass of the Sun. Low-mass stars like Proxima Centauri burn for about 4 trillion years, ~330 times longer than the Sun will.
Proxima Centauri b is close enough to its star that it might be tidally locked, a state in which, over the course of an orbit, no net transfer of angular momentum occurs between a planet and its host star. If the planet’s orbital eccentricity is 0, this could result in synchronous rotation, with one blazing hot side permanently facing towards the star, while the opposite side is permanently dark and freezing cold.
Proxima Centauri b’s orbital eccentricity is not known with certainty, only that it is below 0.35 – potentially high enough for it to have a significant chance of being captured into a 3:2 spin-orbit resonance similar to that of Mercury. The European Southern Observatory predicts that a far more clement environment would result from such a configuration, with average temperatures similar to those on Earth. A large portion of the planet may be habitable if it supports a thick enough atmosphere to transfer heat to the side facing away from the star. Calculations reveal that the planet could have lost about 1 ocean’s worth of water due to the early irradiation in the first 100–200 million years after formation. Liquid water may be present only in the sunniest regions of the planet’s surface.