Proxima Centauri b / Center Objects
Context
Proxima Centauri b (also called Proxima b or Alpha Centauri Cb) is an exoplanet orbiting in the habitable zone of the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of a triple star system. It is approximately 4.2 light-years (4.0×1013 km) from Earth in the constellation Centaurus, making it and Proxima c the closest known exoplanets to the Solar System.
Proxima Centauri b orbits the star at a distance of roughly 0.05 AU (7,500,000 km; 4,600,000 mi) with an orbital period of approximately 11.2 Earth days, and has an estimated mass of at least 1.2 times that of Earth. It is subject to stellar wind pressures of more than 2,000 times those of Earth from the solar wind, and its habitability has not yet been definitively established.
The planet's discovery was announced in August 2016. It was found using the radial velocity method, where periodic Doppler shifts of the parent star's spectral lines suggest an orbiting object. From these readings, the parent star's radial velocity relative to the Earth is varying with an amplitude of about 1.4 metres (4.5 feet) per second. According to Guillem Anglada‐Escudé, the planet's proximity to Earth offers an opportunity for robotic exploration with the Starshot project or, at least, "in the coming centuries".
Without its orbital inclination known, Proxima Centauri b's exact mass is unknown. If its orbit is nearly edge-on, it would have a mass of 1.173±0.086 M⊕ (Earth masses).Statistically, there is a roughly 90% chance that its mass is less than 2.77 M⊕.
In May 2019, a paper presenting recent Spitzer Space Telescope data concluded that Proxima Centauri b did not transit its sun relative to Earth, and attributed previous transit detections to correlated noise