from its photosphere at an effective temperature of 18,445 K. In 1968 the primary was found to have variable radial velocity, which is evidence of a second star in the system, but no orbit was published. The existence of the secondary star, b Centauri B, was confirmed in 2010 with an interferometric observation, which revealed it at a separation of , or at the system's distance. The difference in magnitude between the stars is 1.06, from which a mass of is calculated for the secondary. However this value for the magnitude difference is uncertain, since it was based on a single observation and the detection is close to the instrument performance limit, so the mass of is considered an upper estimate. Given all uncertainties, the total mass of the system is estimated at 6 to . Planetary system The b Centauri system was included in the BEAST survey, which uses the SPHERE instrument at the Very Large Telescope to search for planets around B-type stars in the Scorpius–Centaurus association. SPHERE is equipped with a sophisticated coronagraph that blocks out the light from a star and allows exoplanets around it to be directly imaged. The first observation of the system in 2019 revealed an object at a separation that had infrared colors consistent with a massive planet. A second observation in 2021 confirmed that the object has common proper motion with b Centauri and therefore is physically bound to the system. The authors of this study also looked for old observations of b Centauri and found that the planet had been imaged by the ESO 3.6 m Telescope in 2000, but was considered a background star at the time. With a primary star mass of and a total system mass of , b Centauri is the most massive system around which a planet has been found; previously, the most massive star with a known planet was . The discovery was published in December 2021 on the scientific journal Nature and was led by Stockholm University astronomer Markus Janson. Named b Centauri (AB)b (shortened as 'b Cen (AB)b'), this is a circumbinary planet that orbits the stellar pair at a projected separation of . The three epochs of observations show evidence of the orbital motion of the planet around the central stars, but the orbit is still not well constrained. The data are consistent with an orbital period between 2650 and 7170