Nair al Saif (Iota Orionis)
Iota Orionis is the brightest star in Orion’s sword, of magnitude 2.77, at the tip of the sword. It has the traditional name نير السيف , which means simply “the Point-Brilliance of the Sword” in Arabic. Iota Orionis is a Romanized version of the Greek name ι οριοηις of the Bayer designation. You see, great pain was incurred re-naming stars into Greek then Latin by a German to replace the common-sense Arabic.
To quote Wikipedia: “A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation’s Latin name. The original list of Bayer designations contained 1,564 stars. The brighter stars were assigned their first systematic names by the German astronomer Johann Bayer in 1603…”
In SkySafari Pro 6.0© and other astronomical software, star catalogues, and star charts, the traditional names live on. Why? Part of the reason might be that this region of Orion is “claimed” by amateur astronomers. From its discovery, to its first long-exposure black and white photograph in a burro of London, by a sanitation engineer, amateurs have claimed and re-claimed this birthplace of stars, perhaps.
Iota Orionis is a quadruple star system at an uncertain distance of 1300 light years. The white primary is a class O9 giant, with a temperature of 31,500 K, and is one of the hottest and bluest stars that make up Orion The Hunter’s classical figure. This 15-solar-mass star has the solid luminosity of 14,000 Suns. Yet, a class O9 star should have a luminosity twice that, suggesting that the system’s true distance is closer to 2000 light years. The primary is also a massive spectroscopic binary with a hot class B1 companion. Its unusually eccentric (e=0.764), 29-day orbit takes the pair from 0.8 AU to merely 0.11 AU apart. The collision of stellar winds from these stars makes the system a strong X-ray source. That’s correct. Their solar winds collide, mix, and generate tons of energy, releasing massive amounts of X-rays, as documented in this open access publication, below…
Iota Orionis is a complex multiple system. A blue 7th magnitude class B companion lies 11″ away. An 11th magnitude class A or F main-sequence companion, appearing reddish by contrast, is located 50″ away. With true separations of at least 4400 and 20,000 AU, these have orbital periods at least 75,000 and 700,000 years.
Movement and Evolution (warning- stellar violence may be too much for some viewers) – “Four stars enter, Two stars leave.”
Nair al Saif appears to be a “runaway star,” kicked out of the Trapezium Cluster by a very close encounter between two binaries some 2.5 million years ago, along with AE Aur and μ Col. Two of the four stars were ejected, while the remaining two, instead of being evicted, stayed more or less behind in highly eccentric embrace. Nair al Saif still lingers near the Orion’s Nebula (M42), marking the place of the violent “Thunderdome-like” event. More violence is in store, as the star is fated to explode as a supernova.