Rigel is a blue supergiant star of spectral type B8 la. In the constellation of Orion, Rigel marks the celestial hunter's foot. Its name comes from Arabic, and it means "foot. It has exhausted its hydrogen supplies, and it is expanding even now! Rigel will eventually turn into a red supergiant star. Rigel is an Alpha Cygni variable type of star, and through pulsations, Rigel changes in brightness from magnitude 0.
This makes Rigel between 61, to , times brighter than our Sun. Rigel formed at around 8 million years ago from an interstellar medium of gas and dust. Gravity pulled the swirling gas and dust together and resulted in the brightest star in Orion's constellation, Rigel.
The other three small stars orbiting around Rigel may have come from the same interstellar medium. Even so, Rigel is hundreds of times younger than our Sun. It will be the second-brightest object in the sky after the Sun! These stars are the most recognizable in the sky! Long ago, two rivaling Japanese clans chose these stars as their symbol. It was recorded on the Alfonsine Tables. Puanga was the daughter of Rehua, the chief of all the stars.
Rehua was represented by the star Antares. Rigel is a quadruple star system composed of the primary star, Rigel, designated as Beta Orionis A, a blue supergiant star, and three smaller blue-white main-sequence stars, which are considerably smaller, designated as Rigel Ba, Rigel Bb, and Rigel C. Rigel A has 21 solar masses, Rigel Ba has 3.
Most of these stars orbit one another once every ten days. The stars under Rigel B orbit the primary star once every 18, years. Since we have discovered Rigel, we haven't yet witnessed one such orbit. The star is currently moving through a nebulous area of space, and as a result its light is being reflected off several nearby dust and gas clouds, one notable example being the eerie blue glow of IC Witch Head Nebula.
See the image below: Since Rigel falls close to our line of sight of the Orion Nebula, it is often associated with it, but the fact is that the Orion Nebula is almost twice as far away from Earth as Rigel.
Despite the huge difference in their respective distances, Rigel is considered a member of the Taurus-Orion R1 Association, which is reserved for recently- formed stars that are located closer to the Orion Nebula.
Rigel was recognized as an Alpha Cygni variable in , basically meaning that some parts of its stellar surface are contracting at the same time as others areas are expanding. As a result, the apparent magnitude of Rigel varies from between 0. This process seems to be influenced by the helium conversion process that takes place in the core, thus producing at least some of the observed variations in luminosity. This in turn served as the origin for several more alternative names, among which were the now-obsolete Algebar, and Elgebar.
In south-western Australia, the Wotjobaluk Koori people knew Rigel as Yerrerdet-kurrk, the mother-in-law of Totyerguil Altair , with the distance between the two stars symbolizing the taboo of a man approaching his mother-in-law too closely. Though it appears to the naked eye as a single star, Rigel actually has three other companions. Supergiants such as Riegel, are evolved high-mass stars, larger and more luminous than main-sequence stars.
Blue supergiants are newly evolved from the main sequence, have extremely high luminosities, high mass-loss rates, and are generally unstable.
Many of them become luminous blue variables, with episodes of extreme mass loss. Lower mass blue supergiants continue to expand until they become red supergiants. Rigel is believed to have formed around 8 million years ago. Rigel is estimated to have around 21 solar masses. However, Rigel is losing around 10 million times more mass than the rate of the Sun. It is believed that Rigel has already lost 3 solar masses since it was formed.
The Rigel star system has at least 4 components currently discovered. The blue supergiant has a visual companion, which is likely a close triple star system. A fainter star much farther from Rigel might also be a component. The secondary star is referred to as Rigel B. The angular rotation of Rigel B from Rigel A is 9. It has a visual magnitude of 6. Though, both stars appear to share the same proper motion.
The pair would have a minimum orbital period of around The next companion is named Rigel C. They have a measured separation from component B that varies from less than 0. Recent observations showed the two identical components separated by 0. Their estimated orbital period is 63 years. The two spectroscopic components Rigel Ba and Rigel Bb cannot be resolved in optical telescopes but are known to 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.
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