Alnilam is a large blue supergiant

Blue supergiant

Blue supergiants are supergiant stars of spectral type O or B.They are extremely hot and bright, with surface temperatures of 30,000-50,000 K. They typically have 10 to 50 solar masses on the Hertzsprung-Russell diagram, and can have radii up to about 25 solar radii...

 star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 in the constellation

Constellation

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 of Orion

Orion (constellation)

Orion, often referred to as The Hunter, is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous, and most recognizable constellations in the night sky...

. Its Flamsteed designation

Flamsteed designation

Flamsteed designations for stars are similar to Bayer designations, except that they use numbers instead of Greek letters. Each star is assigned a number and the Latin genitive of the constellation it lies in...

 is 46 Orionis.

It is the 30th brightest star in the sky (the 4th brightest in Orion) and as a blue-white supergiant

Blue supergiant

Blue supergiants are supergiant stars of spectral type O or B.They are extremely hot and bright, with surface temperatures of 30,000-50,000 K. They typically have 10 to 50 solar masses on the Hertzsprung-Russell diagram, and can have radii up to about 25 solar radii...

 it is the most powerful bright star in the sky. Together with Mintaka (Delta Orionis

Delta Orionis

Delta Orionis , traditionally known as Mintaka , is a star some 900 light years distant in the constellation Orion. Together with Zeta Orionis and Epsilon Orionis , the three stars make up the belt of Orion, known by many names across many ancient cultures...

) and Alnitak (Zeta Orionis), the three stars make up the belt of Orion, known by many names across many ancient cultures. Alnilam is the middle star.

It is also one of the 57 stars

Navigational stars

Fifty-eight selected navigational stars are given a special status in the field of celestial navigation. Of the approximately 6,000 stars visible to the naked eye under optimal conditions, the selected stars are among the brightest and span thirty-eight constellations of the celestial sphere from...

 used in celestial navigation

Celestial navigation

Celestial navigation, also known as astronavigation, is a position fixing technique that has evolved over several thousand years to help sailors cross oceans without having to rely on estimated calculations, or dead reckoning, to know their position...

. It is at its highest point in the sky around midnight on December 15.

Alnilam's relatively simple spectrum has made it useful for studying the interstellar medium

Interstellar medium

In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...

. Within the next million years, this star may turn into a red supergiant

Red supergiant

Red supergiants are supergiant stars of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive...

 and explode as a supernova

Supernova

A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...

. It is surrounded by a molecular cloud

Molecular cloud

A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen ....

, NGC 1990

NGC 1990

NGC 1990 is a Reflection nebula which is a molecular cloud of Epsilon Orionis. The stellar winds from Epsilon Orionis, or Alnilam, distribute the nebula approximately up to 2000 km/s, more than 20 million times that of the stellar winds of the Sun....

, which it brightens to make a reflection nebula

Reflection nebula

In Astronomy, reflection nebulae are clouds of dust which are simply reflecting the light of a nearby star or stars. The energy from the nearby star, or stars, is insufficient to ionize the gas of the nebula to create an emission nebula, but is enough to give sufficient scattering to make the dust...

. Its stellar wind

Stellar wind

A stellar wind is a flow of neutral or charged gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.Different types of stars have...

s may reach up to 2000 km/s

Velocity

In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...

, causing it to lose mass

Mass

Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

 about 20 million times more rapidly than the Sun.

Other names and history

The name Alnilam derives from the Arabic

Arabic language

Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 النظام an-niżām, related to the word نظم nażm "string of pearls". Related spellings are Alnihan and Alnitam: all three variants are evidently mistakes in transliteration or copy errors.

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

Chinese mythology

Chinese mythology is a collection of cultural history, folktales, and religions that have been passed down in oral or written tradition. These include creation myths and legends and myths concerning the founding of Chinese culture and the Chinese state...

 they were also known as The Weighing Beam. The belt was also the Three Stars

Three Stars (Chinese constellation)

The Three Stars mansion is one of the twenty-eight mansions of the Chinese constellations. It is one of the western mansions of the White Tiger. This collection of seven bright stars is visible during winter in the Northern Hemisphere .- Asterisms :...

 mansion , one of the Twenty-eight mansions

Twenty-eight mansions

The Twenty-eight Mansions , ', ' or ' are part of the Chinese constellations system. They can be considered as the equivalent to the zodiacal constellations in the Western astronomy, though the Twenty-eight Mansions reflect the movement of the Moon in a lunar month rather than the Sun in a solar year...

 of the Chinese constellation

Chinese constellation

Chinese constellations are the way the ancient Chinese grouped the stars. They are very different from the modern IAU recognized constellations. This is because the IAU was based on Greco-Roman astronomy instead of Chinese astronomy....

s. It is one of the western mansions of the White Tiger.

In pre-Christian Scandinavia

Scandinavia

Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

, the belt was known as Frigg

Frigg

Frigg is a major goddess in Norse paganism, a subset of Germanic paganism. She is said to be the wife of Odin, and is the "foremost among the goddesses" and the queen of Asgard. Frigg appears primarily in Norse mythological stories as a wife and a mother. She is also described as having the power...

's Distaff

Distaff

As a noun, a distaff is a tool used in spinning. It is designed to hold the unspun fibers, keeping them untangled and thus easing the spinning process. It is most commonly used to hold flax, and sometimes wool, but can be used for any type of fiber. Fiber is wrapped around the distaff, and tied in...

 (Friggerock) or Freyja's distaff. Similarly Jacob's Staff and Peter's Staff were European biblical

Bible

The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

 derived terms, as were the Three Magi, or the Three Kings. Väinämöinen

Väinämöinen

Väinämöinen is the central character in the Finnish folklore and the main character in the national epic Kalevala. His name comes from the Finnish word väinämö, meaning minstrel. Originally a Finnish god, he was described as an old and wise man, and he possessed a potent, magical...

's Scythe (Kalevala

Kalevala

The Kalevala is a 19th century work of epic poetry compiled by Elias Lönnrot from Finnish and Karelian oral folklore and mythology.It is regarded as the national epic of Finland and is one of the most significant works of Finnish literature...

) and Kalevan Sword are terms from Finnish mythology

Finnish mythology

Finnish mythology is the mythology that went with Finnish paganism which was practised by the Finnish people prior to Christianisation. It has many features shared with fellow Finnic Estonian mythology and its non-Finnic neighbours, the Balts and the Scandinavians...

.

The Seri people of northwestern Mexico call the three belt stars Hapj (a name denoting a hunter) which consists of three stars: Hap (mule deer), Haamoja (pronghorn), and Mojet (bighorn sheep). Hap is in the middle and has been shot by the hunter; its blood has dripped onto Tiburón Island

Tiburón Island

Tiburón Island is both the largest island in the Gulf of California and the largest island in Mexico, with an area of . It was made a nature reserve in 1963 by President Adolfo López Mateos. Tiburón is Spanish for shark. The etymology of the Seri name is unknown...

.

See also

• Epsilon Orionis in fiction

External links

• Image of Alnilam from APOD
  Astronomy Picture of the Day
  Astronomy Picture of the Day is a website provided by NASA and Michigan Technological University . According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written by a professional astronomer."The photograph is not necessarily...