Estimates of Alnilam's properties vary. Crowther and colleagues, using stellar wind and atmospheric modelling in 2006, came up with a luminosity 275,000 times that of the Sun, and effective temperature of 27,000 K and a radius 24 times that of the Sun. Searle and colleagues, using CMFGEN code to analyse the spectrum in 2008, calculated a luminosity of, an effective temperature of 27,500 ± 100 K and a radius of. Analysis of the spectra and age of the members of the Orion OB1 association yields a mass 34.6 times that of the Sun and an age of 5.7 million years. A more recent detailed analysis of Alnilam across multiple wavelength bands produced very high luminosity, radius, and mass estimates, assuming the distance of 606 parsecs suggested by the Hipparcos new reduction. Adopting the larger parallax from the original Hipparcos reduction gives a distance of 412 parsecs and physical parameters more consistent with earlier publications. The luminosity of at 606 parsecs is the highest ever derived for this star. Alnilam's relatively simple spectrum has made it useful for studying the interstellar medium. Within the next million years, this star may turn into a red supergiant and explode as a supernova. It is surrounded by a molecular cloud, NGC 1990, which it illuminates to make a reflection nebula. Its stellar winds may reach up to 2000 km/s, causing it to lose mass about 20 million times more rapidly than the Sun.
Nomenclature and history
ε Orionis is the star's Bayer designation and 46 Orionis its Flamsteed designation. The traditional name Alnilam derives from the Arabic النظام al-niẓām 'arrangement/string '. Related spellings are Alnihan and Alnitam: all three variants are evidently mistakes in transliteration or copy errors, the first perhaps due to confusion with النيلم al-nilam 'sapphire'. In 2016, the International Astronomical Union organized a Working Group on Star Names to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Alnilam for this star. It is now so entered in the IAU Catalog of Star Names.
Orion's Belt
The three belt stars were collectively known by many names in many cultures. Arabic terms include Al Nijād 'the Belt', Al Nasak 'the Line', Al Alkāt 'the Golden Grains or Nuts', and, in modern Arabic, Al Mīzān al H•akk 'the Accurate Scale Beam'. In Chinese mythology, they were also known as The Weighing Beam. In Chinese, 參宿, meaning Three Stars , refers to an asterism consisting of Alnilam, Alnitak, and Mintaka, with Betelgeuse, Bellatrix, Saiph, and Rigel later added. Consequently, the Chinese name for Alnilam is 參宿二. It is one of the western mansions of the White Tiger.
