Orion (constellation)

Orion

Constellation
List of stars in Orion
Abbreviation	Ori
Genitive	Orionis
Pronunciation	/ɒˈraɪ.ən/
Symbolism	Orion
Right ascension	5 h
Declination	+5°
Quadrant	NQ1
Area	594 sq. deg. (26th)
Main stars	7
Bayer/Flamsteed stars	81
Stars with planets	6
Stars brighter than 3.00m	8
Stars within 10.00 pc (32.62 ly)	8
Brightest star	Rigel (β Orionis) (0.12m)
Nearest star	GJ 3379 (17.51 ly, 5.37 pc)
Messier objects	3
Meteor showers	Orionids Chi Orionids
Bordering constellations	Gemini Taurus Eridanus Lepus Monoceros
Visible at latitudes between +85° and −75°. Best visible at 21:00 (9 p.m.) during the month of January. Credit: Mouser Williams

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.^[1] Its name refers to Orion, a hunter in Greek mythology.

Visualizations

Orion as depicted in Urania's Mirror, a set of constellation cards published in London c.1825.

Orion includes the prominent asterism known as the Belt of Orion: three bright stars in a row. Surrounding the belt at roughly similar distances are four bright stars, which are considered to represent the outline of the hunter's body. Apparently descending from the 'belt' is a smaller line of three stars (the middle of which is in fact not a star but the Orion Nebula), known as the hunter's 'sword'.

In artistic renderings, the surrounding constellations are sometimes related to Orion: he is depicted standing next to the river Eridanus with his two hunting dogs Canis Major and Canis Minor, fighting Taurus the bull. He is sometimes depicted hunting Lepus the hare.

There are alternative ways to visualize Orion. From the Southern Hemisphere, Orion is oriented differently, and the belt and sword are sometimes called the Saucepan, or Pot in Australia/New Zealand. Orion's Belt is called Drie Konings (Three Kings) or the Drie Susters (Three Sisters) by Afrikaans speakers in South Africa,^[2] and are referred to as les Trois Rois (the Three Kings) in Daudet's Lettres de Mon Moulin (1866). The appellation Driekoningen (the Three Kings) is also often found in 17th- and 18th-century Dutch star charts and seaman's guides. The same three stars are known in Spain and Latin America as "The Three Marys".

In the tropics (less than about 8° from the equator) the constellation transits in the zenith which is best seen in Nov-Feb each year. In the northern hemisphere, it is a winter constellation because from Apr-Aug it can only be viewed in the southern hemisphere. However, in Antarctica it is best seen in the winter months of the southern hemisphere, due to the summer sun not setting and therefore no stars are visible. From May-July in the southern hemisphere, Orion is in the 'daytime' sky; however for most of Antarctica, the Sun is below the horizon even at midday, so stars (and thus Orion) are most visible at twilight for a couple of hours around midday low in the North. On the South Pole itself (Amundsen-Scott South Pole Station) only Rigel is 8° above the horizon and the belt sweeps just along the horizon.

Navigational aid

Using Orion to find stars in neighbor constellations

Orion is very useful as an aid to locating other stars. By extending the line of the Belt southeastward, Sirius (α CMa) can be found; northwestward, Aldebaran (α Tau). A line eastward across the two shoulders indicates the direction of Procyon (α CMi). A line from Rigel through Betelgeuse points to Castor and Pollux (α Gem and β Gem). Additionally, Rigel is part of the Winter Circle. Sirius and Procyon, which may be located from Orion by tracing lines, also are points in both the Winter Triangle and the Circle.^[3]

Notable features

Stars

• Betelgeuse, known alternatively by its Bayer designation Alpha Orionis, is a massive M-type red supergiant star nearing the end of its life. When it explodes it will even be visible during the day. It is the second brightest star in Orion, and is a semiregular variable star^[4]. It serves as the "right shoulder" of the hunter it represents (assuming that he is facing the observer), and is the twelfth brightest star in the night sky.^[5]

• Rigel, which is also known as Beta Orionis, is a B-type blue supergiant that is the sixth brightest star in the night sky. Similar to Betelguese, Rigel is fusing heavy elements in its core and will pass its supergiant stage soon (on an astronomical timescale), either collapsing in the case of a supernova or shedding its outer layers and turning into a white dwarf. It serves as the left foot of Orion, the hunter.^[6]

• Bellatrix was designated Gamma Orionis by Johann Bayer, but is known colloquially as the "Amazon Star;" it is the twenty-second brightest star in the night sky.^[7] Bellatrix is considered a B-type blue giant, though it is too small to explode in a supernova. Bellatrix's luminosity is derived from its high temperature rather than its radius,^[8] a factor that defines Betelguese.^[4] Bellatrix serves as Orion's left shoulder.^[8]

• Mintaka garnered the name Delta Orionis from Bayer, even though it is the faintest of the three stars in Orion's Belt. It is a multiple star system, composed of a large B-type blue giant and a more massive O-type white star. The Mintaka system constitutes an eclipsing binary variable star, where the eclipse of one star over the other creates a dip in brightness. Mintaka is the westernmost of the three stars that constitute Orion's Belt.^[9]

• Alnilam was named Epsilon Orionis, a consequence of Bayer's wish to name the three stars in Orion's Belt (from north to south) in alphabetical order. Alnilam is a B-type blue supergiant, despite being nearly twice as far from the Sun as Mintaka and Alnitak, the other two belt stars, its luminosity makes it nearly equal in magnitude. Alnilam is losing mass quickly, a consequence of its size;^[10] approximately four million years old ^[10].

• Alnitak was designated Zeta Orionis by Bayer, and is the easternmost star in Orion's Belt. It is a triple star some 800 light years distant, with the primary star being a hot blue supergiant and the brightest class O star in the night sky.

• Saiph was designated Kappa Orionis by Bayer, and serves as Orion's right foot. It is of a similar distance and size to Rigel, but appears much fainter, as its hot surface temperature (46,000°F or 26,000°C) causes it to emit most of its light in the ultraviolet region of the spectrum.

Of the lesser stars, Hatsya (or Iota Orionis) forms the tip of Orion's sword, whilst Meissa (or Lambda Orionis) forms Orion's head. In common with many other bright stars, the names Betelgeuse, Rigel, Saiph, Alnitak, Mintaka, Alnilam, Hatsya and Meissa originate from the Arabic language.

Belt

Orion's Belt or The Belt of Orion is an astronomical asterism in the constellation Orion. It consists of the three bright stars ζ Ori (Alnitak), ε Ori (Alnilam), and δ Ori (Mintaka). Alnitak is approximately 800 light years away from earth and considering ultraviolet radiation, which human eye can not see, Alnitak is 100,000 times more luminous than the Sun^[11]. Alnilam is approximately 1340 light years away from earth and shines with magnitude 1.70. Considering ultraviolet light Alnilam is 375,000 times more luminous than the Sun^[12]. Mintaka is 915 light years away and shines with magnitude 2.21. Mintaka is 90,000 times more luminous than the Sun. Mintaka is a double star. Both stars orbit around each other every 5.73 days. ^[13] Looking for Orion's Belt in the night sky is the easiest way to locate constellation Orion in the sky. In the Northern hemisphere, Orion's Belt is best visible in the night sky during the month of January at around 9:00 PM when it is approximately around local meridian.^[14]

The same three stars are known in Latin America as "The Three Marys".^[15] They also mark the northern night sky when the sun is at its lowest point, and were a clear marker for ancient timekeeping.

Richard Hinckley Allen lists many folk names for the Belt of Orion. The English ones include: Jacob's Rod or Staff; Peter's Staff; the Golden Yard-arm; the L, or Ell; the Ell and Yard; the Yard-stick, and the Yard-wand; the Ellwand; Our Lady's Wand; the Magi; the Three Kings; the Three Marys; or simply the Three Stars.

The passage "Canst thou bind the sweet influences of Pleiades, or loose the bands of Orion?" is found in the Bible's Book of Job.

Closeup Image of Orion Belt.

Orion Constellation Map.

The Belt of Orion.

The region of Orion’s Belt and the Flame Nebula.

Meteor showers

Around October 21 each year the famous Orionid meteor shower reaches its peak. Coming from the border to the constellation Gemini as much as 20 meteors per hour can be seen.

Deep sky objects

Hanging from Orion's belt is his sword, consisting of the multiple stars θ1 and θ2 Orionis, called Trapezium and the Orion Nebula (M42). This is a spectacular object which can be clearly identified with the naked eye as something other than a star; using binoculars, its swirling clouds of nascent stars, luminous gas, and dust can be observed.

Another famous nebula is IC 434, the Horsehead Nebula, near ζ Orionis. It contains a dark dust cloud whose shape gives the nebula its name.

Besides these nebulae, surveying Orion with a small telescope will reveal a wealth of interesting deep sky objects, including M43, M78, as well as multiple stars including Iota Orionis and Sigma Orionis. A larger telescope may reveal objects such as Barnard's Loop, the Flame Nebula (NGC 2024), as well as fainter and tighter multiple stars and nebulae.

All of these nebulae are part of the larger Orion Molecular Cloud Complex which is located approximately 1,500 light-years away and is hundreds of light-years across. It is one of the most intense regions of stellar formation visible in our galaxy.

Cultural significance

Star formation in the constellation Orion as photographed in infrared by NASA's Spitzer Space Telescope.

The current configuration of stars now known as the constellation of Orion roughly formed about 1.5 million years ago, as stars move relatively slowly from the perspective of Earth. Orion will remain recognizable in the night sky for the next 1 to 2 million years, making it one of the longest observable constellations, parallel to the rise of human civilization.

Because they are so bright and distinctive, the pattern of stars that forms Orion was recognized as a coherent constellation by many ancient civilizations, though with different representations and mythologies.

Ancient Near East

The Babylonian star catalogues of the Late Bronze Age name Orion ^MULSIPA.ZI.AN.NA, "The Heavenly Shepherd".^[16]

The Bible mentions Orion three times: Job 9:9 ("He is the maker of the Bear and Orion"), Job 38:31 ("Can you loosen Orion`s belt?"), and Amos 5:8 ("He who made the Pleiades and Orion"). In ancient Aram, the constellation was known as Nephila, Orion's descendants were known as Nephilim.^[17]

The stars were associated with Osiris, the god of rebirth and afterlife, by the ancient Egyptians.^[18]

Orion has also been identified with the last Egyptian Pharaoh of the Fifth Dynasty called Unas who, according to the Pyramid Texts, became great by eating the flesh of his mortal enemies and then slaying and devouring the gods themselves. This was based on a belief in contiguous magic whereby consuming the flesh of great people would bring inheritance of their power.^[19] After devouring the gods and absorbing their spirits and powers, Unas journeys through the day and night sky to become the star Sabu, or Orion.^[20] The Pyramid Texts also show that the dead Pharaoh was identified with the god Osiris, whose form in the stars was often said to be the constellation Orion.^[21]

Greek and Roman

Orion's current name derives from Greek mythology, in which Orion was a gigantic hunter of primordial times^[22]. Some of these myths relate to the constellation; one story tells that Orion was killed by a giant scorpion; the gods raised him and the Scorpion to the skies, as Scorpio/Scorpius. Yet other stories say Orion was chasing the Pleiades.^[23]

The constellation is mentioned in Horace's Odes, Homer's Odyssey (Book 5, line 283) and Iliad, and Virgil's Aeneid (Book 1, line 535)

Hungarian

In ancient Hungarian mythology, Orion is also a great hunter and warrior, his name is Nimród and he's the mythological father of Hungarians.

Scandinavia

In pre-Christian Scandinavia, "Orion's belt" was known as Frigg's Distaff (Friggerock) or Freyja's distaff^[24].

In Finnish mythology the constellation of Orion is called the scythe of Väinämöinen. The term most likely comes from the fact that it can be seen in the sky in early autumn in the Northern Hemisphere, the time of harvesting crops.

Indian

In Indian mythology, the Rig Veda refers to the Orion Constellation as Mriga (The Deer).^[25]

Chinese

In China, Orion was one of the 28 lunar mansions Sieu (Xiu) （宿）. Known as Shen （參）, literally meaning "three", it is believed to be named so for the three stars located in Orion's belt. (See Chinese constellations)

The Chinese character 參 (pinyin shēn) originally meant the constellation Orion (Chinese: 參宿; pinyin: shēnxiù); its Shang dynasty version, over three millennia old, contains at the top a representation of the three stars of Orion's belt atop a man's head (the bottom portion representing the sound of the word was added later)^[26].

Native American

The Yokut Native American tribe of the California Central Valley saw the three bright stars as the foot prints of the god of the flea people. According to legend, when his five wives became itchy and ran away, three times the god of the flea people jumped into the sky to look for them. When his footprints are seen (stars are visible in the winter months) the flea people grow afraid and go into hiding (i.e. dormant). This helped explain to the tribal people why they couldn't count on those stars for guides in the summer months, and why there were no fleas about.

The Seri people of northwestern Mexico call the three stars in the belt of this constellation 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.^[27]

The Aztecs called the belt and sword of Orion the Fire Drill. Its appearance over the horizon served as the signal of the start of the New Fire ceremony.

Australian aboriginal

Orion is also important in Australian Aboriginal Astronomy. For example, the Yolngu people of Arnhem Land say that the constellation of Orion, which they call Julpan, is a canoe. They tell the story of two brothers who went fishing, and caught and ate a fish that was forbidden under their law. Seeing this, the Sun sent a waterspout that carried the two brothers and their canoe up into the sky where they became the Orion constellation.

Contemporary symbolism

The imagery of the belt and sword has found its way into popular western culture, for example in the form of the shoulder insignia of the 27th Infantry Division of the United States Army during both World Wars, probably owing to a pun on the name of the division's first commander, Major General John F. O'Ryan.

The defunct film distribution company Orion Pictures used the constellation as its logo.

Future

Orion is presently located on the celestial equator, but it will not always be so located due to the effects of precession of the Earth's axis. Orion lies well south of the ecliptic, and it only happens to lie on the celestial equator because the point on the ecliptic that corresponds to the June solstice is close to the border of Gemini and Taurus, to the north of Orion. Precession will eventually carry Orion further south, and by 14,000 CE Orion will be far enough south that it will become invisible from the latitude of Great Britain ^[28].

Further in the future, Orion's stars will gradually move away from the constellation due to proper motion. However, Orion's brightest stars all lie at a large distance from the Earth on an astronomical scale. (For example, they are much farther away than Sirius is.) Orion will still be recognisable long after most of the other constellations - composed of relatively nearby stars - have distorted into new configurations, with the exception of a few of its stars eventually exploding as supernovae. For example, Betelgeuse, the "right shoulder", is so large and old enough that it may explode and disappear within a few thousand years.

See also

• Orvandil
• Orion Correlation Theory

Notes

References

• Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0007251209. Princeton University Press, Princeton. ISBN 978-0691135564.

External links

• The Deep Photographic Guide to the Constellations: Orion
• Melbourne Planetarium: Orion Sky Tour
• The clickable Orion
• Star Tales – Orion

Coordinates: 05^h 30^m 00^s, +00° 00′ 00″