Orion’s Belt

StarDate: -314224.72

The rainy Pleiads wester,
Orion plunges prone,
The stroke of midnight ceases,
And I lie down alone.

A. E. Housman

Orion’s Belt and M42 (The Orion Nebula)

This diary continues our previous visit to Orion. I hope you find it interesting and informative. This time we take a look at the 3 stars of the Belt of Orion.

Orion, The Hunter, is a famous, easily recognizeable constellation located along the celestial equator which is visible from both the northern and southern hemispheres. In the northern hemisphere it is a winter constellation, visible in the night sky from November through February. The constellation contains 6 of the top 100 brightest stars in the sky.

Section of a plate from Uranographia
showing the constellation Orion by
Johann Elert Bode

The three stars that make the Belt of Orion (delta, epsilon, and zeta Orionis) are known by various cultures by many different names. Western culture passes the name of “Orion’s Belt” down to us.

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’. W ik i

From the Southern Hemisphere Orion is, of course, oriented differently, and different cultures there as in the Northern Hemisphere have different appelations for the constellation. For example, the stars of Orion’s belt are called Drie Konings (Three Kings) in Afrikaans speakers of South Africa Wiki, probably related to the name that appeared on 17th and 18th century Dutch star and navigational charts.

In Chinese mythology they were also known as The Weighing Beam.[1] The belt was also the Three Stars mansion (traditional Chinese: &#x53c3宿 simplified Chinese: &#x53c2宿 pinyin: Sh&#x0113n Xiù), one of the Twenty-eight mansions of the Chinese constellations. It is one of the western mansions of the White Tiger.

In pre-Christian Scandinavia, the belt was known as Frigg’s Distaff (Friggerock) or Freyja’s distaff[2]. Similarly Jacob’s Staff and Peter’s Staff were European biblical derived terms, as were the Three Magi, or the Three Kings. Väinämöinen’s Scythe (Kalevala) and Kalevan Sword are terms from Finnish mythology.

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. W ik i

The star’s along Orion’s belt can be used to locate two other notable stars of the night sky, Sirius and Aldebaran. Sirius, along the line (almost directly) to the southeast is the brightest star in the sky. Aldebaran, along the line in the opposite direction is the 13th brightest star.

Mintaka is at the upper left.
Credit: Digitized Sky Survey,
ESA/ESO/NASA FITS Liberator

Mintaka (δ Ori, δ Orionis)

Mintaka is the seventh brightest of the stars in Orion. The furthest west and faintest of the three stars of Orion’s belt it is approximately 900 light years from Earth. The name Mintaka comes from the Arabic for “belt” ( منطق ة, manţaqah )¹.

Mintaka is a binary star system consisting of two very hot stars of about 20 solar masses each. The larger of the two is a type B star, the smaller a type O. These stars are about 70,000 times as luminous as the Sun. The orbital period of the two stars is 5.73 days with a maximum separation of 0.03 seconds of arc. The Mintaka system also includes 2 smaller dimmer stars which orbit the prim-

ary binary stars at 0.25 light years with of magnitude 6.8 and another even closer in at magnitude 14.

Mintaka played a role in the STNG episode Who Watches the Watchers. Mintaka III being the home of a proto-Vulcan race that were being observed by Federation scientists.

Alnilam (ε Ori, ε Orionis)

Alnilam is the 30th brightest star in the sky and the fourth brightest of the Constellation of Orion. It is a massive (40 solar masses) blue-white supergiant and is one of the most luminous stars known at ~375,000 L_☉. It is surrounded by a nebular cloud (ncg 1990) which it illuminates creating a reflection nebula (as can be seen in the accompanying photo.

Alnilam takes its name from the Arabic an-niżām¹ ( النظام ) which can be translated as “string of pearls”.

Epsilon Orionis is one of the 57 navigational stars which is at its highest point at midnight on December 15th.

Alnilam lights up NGC 1990.
Photograph by Glen Youman.

Atlas Image courtesy of 2MASS/UMass/IPAC-Caltech/NASA/NSF

Alnitak (ζ Ori, ζ Orionis)

Alnitak is a triple star system at a distance of 800 ly from Earth. The primary of the system is a class O blue supergiant with a mass of approximately 28 solar masses. Its two companion stars are 4th magnitude blue stars. Alnitak B has an orbital period of 1500 years and is a type B star. The recently discovered Alnitak ab is a O class star.

Alnitak is a triple star system at a distance of 800 ly from Earth. The primary of the system is a class O blue supergiant with a mass of approximately 28 suns and a diameter around 20 times that of the sun.