north at a position angle of 1°. Gaia DR2 finds it to be a 12th magnitude sunlike star at approximately the same distance as Rigel. Likely a K-type main-sequence star, this star would have an orbital period of around 250,000 years, if it is part of the Rigel system. A spectroscopic companion to Rigel was reported on the basis of radial velocity variations, and its orbit was even calculated, but subsequent work suggests the star does not exist and that observed pulsations are intrinsic to Rigel itself. Physical characteristics Rigel is a blue supergiant that has exhausted the hydrogen fuel in its core, expanded and cooled as it moved away from the main sequence across the upper part of the Hertzsprung–Russell diagram. When it was on the main sequence, its effective temperature would have been around . Rigel's complex variability at visual wavelengths is caused by stellar pulsations similar to those of Deneb. Further observations of radial velocity variations indicate that it simultaneously oscillates in at least 19 non-radial modes with periods ranging from about 1.2 to 74 days. Estimation of many physical characteristics of blue supergiant stars, including Rigel, is challenging due to their rarity and uncertainty about how far they are from the Sun. As such, their characteristics are mainly estimated from theoretical stellar evolution models. Its effective temperature can be estimated from the spectral type and color to be around . A mass of at an age of million years has been estimated by comparing evolutionary tracks, while atmospheric modeling from the spectrum gives a mass of . Although Rigel is often considered the most luminous star within 1,000 light-years of the Sun, its energy output is poorly known. Using the Hipparcos distance of , the estimated relative luminosity for Rigel is about 120,000 times that of the Sun (), but another recently published distance of suggests an even higher luminosity of . Other calculations based on theoretical stellar evolutionary models of Rigel's atmosphere give luminosities anywhere between and , while summing the spectral energy distribution from historical photometry with the Hipparcos distance suggests a luminosity as low as . A 2018 study using the Navy Precision Optical Interferometer measured the angular diameter as . After correcting for limb darkening, the angular diameter is found to be , yielding a radius of . An older measurement of the angular diameter gives , equivalent to a radius of