B or β Orionis B. The angular separation of Rigel B from Rigel A is 9.5 arc seconds to its south along position angle 204°. Although not particularly faint at visual magnitude 6.7, the overall difference in brightness from Rigel A (about 6.6 magnitudes or 440 times fainter) makes it a challenging target for telescope apertures smaller than . At Rigel's estimated distance, Rigel B's projected separation from Rigel A is over 2,200astronomical units (AU). Since its discovery, there has been no sign of orbital motion, although both stars share a similar common proper motion. The pair would have an estimated orbital period of 24,000years. Gaia Data Release 2(DR2) contains a somewhat unreliable parallax for Rigel B, placing it at about , further away than the Hipparcos distance for Rigel, but similar to the Taurus-Orion R1 association. There is no parallax for Rigel in Gaia DR2. The Gaia DR2 proper motions for Rigel B and the Hipparcos proper motions for Rigel are both small, although not quite the same. In 1871, Sherburne Wesley Burnham suspected Rigel B to be a binary system, and in 1878, he resolved it into two components. This visual companion is designated as component C (Rigel C), with a measured separation from component B that varies from less than to around . In 2009, speckle interferometry showed the two almost identical components separated by , with visual magnitudes of 7.5 and 7.6, respectively. Their estimated orbital period is 63years. Burnham listed the Rigel multiple system as β555 in his double star catalog or BU555 in modern use. Component B is a double-lined spectroscopic binary system, which shows two sets of spectral lines combined within its single stellar spectrum. Periodic changes observed in relative positions of these lines indicate an orbital period of 9.86days. The two spectroscopic components Rigel Ba and Rigel Bb cannot be resolved in optical telescopes but are known to both be hot stars of spectral type around B9. This spectroscopic binary, together with the close visual component Rigel C, is likely a physical triple-star system, although Rigel C cannot be detected in the spectrum, which is inconsistent with its observed brightness. In 1878, Burnham found another possibly associated star of approximately 13th magnitude. He listed it as component D of β555, although it is unclear whether it is physically related or a coincidental alignment. Its 2017 separation from Rigel was , almost due