A fainter star at a wider separation might be a fifth component of the Rigel system. William Herschel discovered Rigel to be a visual double star on 1 October 1781, cataloguing it as star 33 in the "second class of double stars" in his Catalogue of Double Stars, usually abbreviated to HII33, or as H233 in the Washington Double Star Catalogue.
Friedrich Georg Wilhelm von Struve first measured the relative position of the companion in 1822, cataloguing the visual pair as Σ 668.
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.
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 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.
Variations in the spectrum have resulted in the assignment of different classes to Rigel, such as B8 Ia, B8 Iab, and B8 Iae. As early as 1888, the heliocentric radial velocity of Rigel, as estimated from the Doppler shifts of its spectral lines, was seen to vary.
The two powerful families fought the Genpei War; the stars were seen as facing off against each other and kept apart only by the three stars of Orion's Belt. == In modern culture == The MS Rigel was originally a Norwegian ship, built in Copenhagen in 1924.
The overall picture is one of large looping structures arising from the photosphere and driven by magnetic fields. === Variability === Rigel has been known to vary in brightness since at least 1930.
The radial velocity has since been measured to vary by about around a mean of . In 1933, the Hα line in Rigel's spectrum was seen to be unusually weak and shifted towards shorter wavelengths, while there was a narrow emission spike about to the long wavelength side of the main absorption line.
It was requisitioned by the Germans during World War II and sunk in 1944 while being used to transport prisoners of war.
The SSM-N-6 Rigel was a cruise missile program for the US Navy that was cancelled in 1953 before reaching deployment. The Rigel Skerries are a chain of small islands in Antarctica, renamed after originally being called Utskjera.
Observations over 18 nights in 1984 showed variations at red, blue, and yellow wavelengths of up to 0.13 magnitudes on timescales of a few hours to several days, but again no clear period.
More detailed optical and Kband infrared spectroscopic observations, together with VLTI interferometry, were taken from 2006 to 2010.
Calculations of mass loss from the Hγ line give in 2006-7 and in 2009–10.
The 2007 Hipparcos new reduction of Rigel's parallax is , giving a distance of with a margin of error of about 9%.
Rigel was observed with the Canadian MOST satellite for nearly 28 days in 2009.
Calculations of mass loss from the Hγ line give in 2006-7 and in 2009–10.
In 2009, speckle interferometry showed the two almost identical components separated by , with visual magnitudes of 7.5 and 7.6, respectively.
More detailed optical and Kband infrared spectroscopic observations, together with VLTI interferometry, were taken from 2006 to 2010.
A much fainter star, separated from Rigel and the others by nearly an arc minute, may be part of the same star system. == Nomenclature == In 2016, the International Astronomical Union (IAU) included the name "Rigel" in the IAU Catalog of Star Names.
Its 2017 separation from Rigel was , almost due north at a position angle of 1°.
A 2018 study using the Navy Precision Optical Interferometer measured the angular diameter as .
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