From May to July (summer in the Northern Hemisphere, winter in the Southern Hemisphere), Orion is in the daytime sky and thus invisible at most latitudes. However, for much ofAntarctica in the Southern Hemisphere's winter months, theSun is below thehorizon even at midday. Stars (and thus Orion, but only the brightest stars) are then visible attwilight for a few hours around local noon, just in the brightest section of the sky low in the North where the Sun is just below the horizon. At the same time of day at the South Pole itself (Amundsen–Scott South Pole Station),Rigel is only 8° above the horizon, and theBelt sweeps just along it. In the Southern Hemisphere's summer months, when Orion is normally visible in the night sky, the constellation is actually not visible in Antarctica because the Sun does not set at that time of year south of theAntarctic Circle.[5][6]
In countries close to theequator (e.g.Kenya,Indonesia,Colombia,Ecuador), Orion appears overhead in December around midnight and in the February evening sky.
Using Orion to find stars in neighbor constellations
Orion is very useful as an aid to locating other stars. By extending the line of theBelt southeastward,Sirius (αCMa) can be found; northwestward,Aldebaran (αTau). A line eastward across the two shoulders indicates the direction ofProcyon (αCMi). A line fromRigel throughBetelgeuse points toCastor andPollux (αGem and β Gem). Additionally, Rigel is part of theWinter Circle asterism. Sirius and Procyon, which may be located from Orion by following imaginary lines (see map), also are points in both theWinter Triangle and the Circle.[7]
Orion's seven brightest stars form a distinctivehourglass-shaped asterism, or pattern, in thenight sky. Four stars—Rigel,Betelgeuse,Bellatrix, andSaiph—form a large roughly rectangular shape, at the center of which lie the three stars ofOrion's Belt—Alnitak,Alnilam, andMintaka. His head is marked by an additional eighth star calledMeissa, which is fairly bright to the observer. Descending from the Belt is a smaller line of three stars,Orion's Sword (the middle of which is in fact not a star but theOrion Nebula), also known as the hunter's sword.
Many of the stars are luminous hotblue supergiants, with the stars of the Belt and Sword forming theOrion OB1 association. Standing out by its red hue, Betelgeuse may nevertheless be a runaway member of the same group.
Stars of the constellation by distance (red-green 3D view) and the brightness of each star (star size)
Bright stars
Betelgeuse, alsodesignated Alpha Orionis, is a massiveM-typered supergiant star nearing the end of its life. It is the second-brightest star in Orion, and is asemiregular variable star.[8] It serves as the right shoulder of the hunter (assuming that he is facing the observer). It is generally the 11th-brightest star in the night sky, but this has varied between being the tenth to the 23rd-brightest by the end of 2019.[9][10] The end of its life is expected to result in asupernova explosion that will be highly visible fromEarth, possibly outshining theMoon and being visible during the day. This is most likely to occur within the next 100,000 years.[11]
Rigel, also known as Beta Orionis, is aB-typeblue supergiant that is the seventh-brightest star in the night sky. Similar to Betelgeuse, Rigel isfusing heavy elements in its core and will pass itssupergiant stage soon (on an astronomical timescale), possibly eventually ending in a supernova explosion. It serves as the left foot of the hunter.[12]
Bellatrix is designated Gamma Orionis byJohann Bayer. It is the 27th-brightest star in the night sky. Bellatrix is considered a B-typeblue giant, though it is too small to explode in a supernova. Bellatrix's luminosity is derived from its high temperature rather than a large radius.[13] Bellatrix marks Orion's left shoulder. Its name means "the female warrior", and is sometimes known colloquially as the "Amazon Star".[14] It is the closest major star in Orion at only 244.6light-years from theSolar System.
Mintaka is designated Delta Orionis, despite being the faintest of the three stars inOrion's Belt. Its name means "the belt". It is amultiple star system, composed of a large B-type blue giant and a more massiveO-typemain sequence star. The Mintaka system constitutes aneclipsing 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 of Orion's Belt, as well as the northernmost.[7]
Alnilam is designated Epsilon Orionis and is named for theArabic phrase meaning "string of pearls".[7] It is the middle and brightest of the three stars of Orion's Belt. Alnilam is a B-type blue supergiant; despite being nearly twice as far from theSun as the other stars on the Belt, its luminosity makes it nearly equal in magnitude. Alnilam is losing mass quickly, a consequence of its size. It is the farthest major star in Orion, at 1,344 light-years.
Alnitak, meaning "thegirdle", is designated Zeta Orionis, and is the easternmost star in Orion's Belt. It is atriple star system, with the primary star being a hot blue supergiant and the brightest O-type star in the night sky.
Saiph is 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. It name means "the sword of the giant".
Meissa is designated Lambda Orionis, forms Orion's head, and is a multiple star with a combinedapparent magnitude of 3.33. Its name means "the shining one".
Orion's Belt, or The Belt of Orion, is anasterism within theconstellation. It consists of three bright stars:Alnitak (Zeta Orionis),Alnilam (Epsilon Orionis), andMintaka (Delta Orionis). Alnitak is around 800light-years away fromEarth, 100,000 times more luminous than theSun, and shines with a magnitude of 1.8; much of its radiation is in theultraviolet range, which the human eye cannot see.[15] Alnilam is approximately 2,000 light-years from Earth, shines with a magnitude of 1.70, and with an ultraviolet light that is 375,000 times more luminous than the Sun.[16] Mintaka is 915 light-years away and shines with a magnitude of 2.21. It is 90,000 times more luminous than the Sun and is adouble star: the two orbit each other every 5.73 days.[17] In theNorthern Hemisphere, Orion's Belt is best visible in thenight sky during the month of January at around 9:00 pm, when it is approximately around the localmeridian.[18]
Just southwest of Alnitak liesSigma Orionis, amultiple star system composed of five stars that have a combined apparent magnitude of 3.7 and lying at a distance of 1150 light-years. Southwest of Mintaka lies the quadruple starEta Orionis.
Three stars comprise a small triangle that marks the head. The apex is marked byMeissa (Lambda Orionis), a hotblue giant of spectral type O8 III and apparent magnitude 3.54, which lies some 1100 light-years distant. Phi-1 and Phi-2 Orionis make up the base. Also nearby is the young starFU Orionis.
Club
Stretching north fromBetelgeuse are the stars that make up Orion's club.Mu Orionis marks the elbow,Nu andXi mark the handle of the club, andChi1 andChi2 mark the end of the club. Just east of Chi1 is the Mira-typevariablered giant starU Orionis.
Around 20 October each year, theOrionid meteor shower (Orionids) reaches its peak. Coming from the border with the constellationGemini, as many as 20 meteors per hour can be seen. The shower's parent body isHalley's Comet.[19]
Deep-sky objects
This view brings out many fainter features, such asBarnard's Loop.Wider view (50° x 39 °) from the Northern Sky Narrowband Survey showing most of theOrion–Eridanus Superbubble.
Hanging fromOrion's Belt is his sword, consisting of themultiple stars θ1 andθ2 Orionis, called theTrapezium and theOrion Nebula (M42). This is a spectacular object that can be clearly identified with the naked eye as something other than a star. Usingbinoculars, its clouds of nascent stars, luminous gas, and dust can be observed. The Trapezium cluster has many newborn stars, including severalbrown dwarfs, all of which are at an approximate distance of 1,500 light-years. Named for the four bright stars that form atrapezoid, it is largely illuminated by the brightest stars, which are only a few hundred thousand years old. Observations by theChandra X-ray Observatory show both the extreme temperatures of the main stars—up to 60,000kelvins—and thestar forming regions still extant in the surrounding nebula.[20]
M78 (NGC 2068) is a nebula in Orion. With an overall magnitude of 8.0, it is significantly dimmer than the Great Orion Nebula that lies to its south; however, it is at approximately the same distance, at 1600 light-years fromEarth. It can easily be mistaken for acomet in the eyepiece of atelescope. M78 is associated with thevariable star V351 Orionis, whose magnitude changes are visible in very short periods of time.[21] Another fairly bright nebula in Orion isNGC 1999, also close to the Great Orion Nebula. It has an integrated magnitude of 10.5 and is 1500 light-years from Earth. The variable starV380 Orionis is embedded in NGC 1999.[22]
Another famousnebula isIC 434, theHorsehead Nebula, nearAlnitak (Zeta 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, includingM43,M78, and multiple stars includingIota Orionis andSigma Orionis. A larger telescope may reveal objects such as theFlame Nebula (NGC 2024), as well as fainter and tighter multiple stars and nebulae.Barnard's Loop can be seen on very dark nights or usinglong-exposure photography.
All of these nebulae are part of the largerOrion molecular cloud complex, which is located approximately 1,500 light-years away and is hundreds of light-years across. Due to its proximity, it is one of the most intense regions of stellar formation visible from Earth. The Orion molecular cloud complex forms the eastern part of an even larger structure, theOrion–Eridanus Superbubble, which is visible in X-rays and in hydrogen emissions.
History and mythology
The distinctive pattern of Orion is recognized in numerous cultures around the world, and many myths are associated with it. Orion is used as a symbol in the modern world.
Ancient Near East
Artwork of the constellation Orion
TheBabylonian star catalogues of theLate Bronze Age name OrionMULSIPA.ZI.AN.NA,[note 1] "The Heavenly Shepherd" or "True Shepherd of Anu" – Anu being the chief god of the heavenly realms.[23] The Babylonian constellation is sacred toPapshukal andNinshubur, both minor gods fulfilling the role of "messenger to the gods". Papshukal is closely associated with the figure of a walkingbird on Babylonian boundary stones, and on the star map the figure of theRooster is located below and behind the figure of the True Shepherd—both constellations represent the herald of the gods, in his bird and human forms respectively.[24]
Inancient Egypt, the stars of Orion were regarded as agod, calledSah. Because Orion rises beforeSirius, the star whoseheliacal rising was the basis for theSolarEgyptian calendar, Sah was closely linked withSopdet, the goddess who personified Sirius. The godSopdu is said to be the son of Sah and Sopdet. Sah issyncretized withOsiris, while Sopdet is syncretized with Osiris' mythological wife,Isis. In thePyramid Texts, from the 24th and 23rd centuries BC, Sah is one of many gods whose form the deadpharaoh is said to take in the afterlife.[25]
TheArmenians identified their legendary patriarch and founderHayk with Orion.Hayk is also the name of the Orion constellation in the Armenian translation of theBible.[26]
The Bible mentions Orion three times, naming it "Kesil" (כסיל, literally – fool). Though, this name perhaps is etymologically connected with "Kislev", the name for the ninth month of the Hebrew calendar (i.e. November–December), which, in turn, may derive from the Hebrew root K-S-L as in the words "kesel, kisla" (כֵּסֶל, כִּסְלָה, hope, positiveness), i.e. hope for winter rains.:Job 9:9 ("He is the maker of the Bear and Orion"), Job 38:31 ("Can you loosen Orion's belt?"), andAmos 5:8 ("He who made thePleiades and Orion").
In ancientAram, the constellation was known asNephîlā′, theNephilim are said to be Orion's descendants.[27]
InGreek mythology, Orion was a gigantic, supernaturally strong hunter,[28] born toEuryale, aGorgon, andPoseidon (Neptune), god of the sea. One myth recountsGaia's rage at Orion, who dared to say that he would kill every animal on Earth. The angry goddess tried to dispatch Orion with ascorpion. This is given as the reason that the constellations ofScorpius and Orion are never in the sky at the same time. However,Ophiuchus, the Serpent Bearer, revived Orion with anantidote. This is said to be the reason that the constellation of Ophiuchus stands midway between the Scorpion and the Hunter in the sky.[29]
As depicted in the 962 A.D. Persian astronomical textBook of Fixed Stars. In this representation Orion is shown as on a globe, so it appears reversed by comparison with its appearance in the sky.
In medievalMuslim astronomy, Orion was known asal-jabbar, "the giant".[30] Orion's sixth brightest star,Saiph, is named from the Arabic,saif al-jabbar, meaning "sword of the giant".[31]
InChina, Orion was one of the28 lunar mansionsSieu (Xiù) (宿). It is known asShen (參), literally meaning "three", for the stars ofOrion's Belt.TheChinese character 參 (pinyin shēn) originally meant the constellation Orion (Chinese:參宿;pinyin:shēnxiù); itsShang 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).[32]
India
TheRigveda refers to the constellation asMriga (theDeer).[33]
Nataraja, "the cosmic dancer", is often interpreted as the representation of Orion.Rudra, the Rigvedic form ofShiva, is the presiding deity of Ardra nakshatra (Betelgeuse) ofHindu astrology.[34]
Bugis sailors identified the three stars inOrion's Belt astanra tellué, meaning "sign of three".[36]
European folklore
In oldHungarian tradition, Orion is known as "Archer" (Íjász), or "Reaper" (Kaszás). In recently rediscovered myths, he is calledNimrod (Hungarian:Nimród), the greatest hunter, father of the twinsHunor and Magor. The π and o stars (on upper right) form together thereflex bow or the lifted scythe. In other Hungarian traditions,Orion's Belt is known as "Judge's stick" (Bírópálca).[37]
TheFinns call Orion's Belt and the stars below it "Väinämöinen'sscythe" (Väinämöisen viikate).[42] Another name for theasterism ofAlnilam,Alnitak, andMintaka is "Väinämöinen's Belt" (Väinämöisen vyö) and the stars "hanging" from the Belt as "Kaleva'ssword" (Kalevanmiekka).
InSiberia, theChukchi people see Orion as a hunter; anarrow he has shot is represented byAldebaran (Alpha Tauri), with the same figure as other Western depictions.[43]
There are claims in popular media that theAdorant from the Geißenklösterle cave, an ivory carving estimated to be 35,000 to 40,000 years old, is the first known depiction of the constellation. Scholars dismiss such interpretations, saying that perceived details such as a belt and sword derive from preexisting features in the grain structure of the ivory.[44][45][46][47]
The Ojibwa/Chippewa Native Americans call this constellation Mesabi for Big Man.[50]
To theLakota Native Americans, Tayamnicankhu (Orion's Belt) is the spine of abison. The great rectangle of Orion is the bison's ribs; thePleiadesstar cluster in nearbyTaurus is the bison's head; andSirius inCanis Major, known as Tayamnisinte, is its tail. Another Lakota myth mentions that the bottom half of Orion, the Constellation of the Hand, represented the arm of a chief that was ripped off by theThunder People as a punishment from the gods for his selfishness. His daughter offered to marry the person who can retrieve his arm from the sky, so the young warrior Fallen Star (whose father was a star and whose mother was human) returned his arm and married his daughter, symbolizing harmony between the gods and humanity with the help of the younger generation. The index finger is represented byRigel; theOrion Nebula is the thumb; the Belt of Orion is the wrist; and the starBeta Eridani is the pinky finger.[51]
The seven primary stars of Orion make up thePolynesian constellation Heiheionakeiki which represents a child's string figure similar to acat's cradle.[52] Severalprecolonial Filipinos referred to the belt region in particular as "balatik" (ballista) as it resembles a trap of the same name which fires arrows by itself and is usually used for catchingpigs from the bush.[53][54][55][56]Spanish colonization later led to some ethnic groups referring toOrion's Belt as "Tres Marias" or "Tatlong Maria."[57]
InMāori tradition, the starRigel (known asPuanga orPuaka) is closely connected with the celebration ofMatariki. The rising of Matariki (thePleiades) and Rigel before sunrise in midwinter marks the start of the Māori year.[58]
In artistic renderings, the surrounding constellations are sometimes related to Orion: he is depicted standing next to theriverEridanus with his twohunting dogsCanis Major andCanis Minor, fightingTaurus. He is sometimes depicted huntingLepus thehare. He sometimes is depicted to have alion's hide in his hand.
There are alternative ways to visualise Orion. From theSouthern Hemisphere, Orion is oriented south-upward, and theBelt andSword are sometimes called thesaucepan or pot inAustralia andNew Zealand. Orion's Belt is calledDrie Konings (Three Kings) or theDrie Susters (Three Sisters) byAfrikaans speakers inSouth Africa[63] and are referred to asles Trois Rois (the Three Kings) inDaudet'sLettres de Mon Moulin (1866). The appellationDriekoningen (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 inSpain,Latin America, and thePhilippines as "Las Tres Marías" (The Three Marys), and as "Los Tres Reyes Magos" (The Three Wise Men) inPuerto Rico.[49]
Even traditional depictions of Orion have varied greatly.Cicero drew Orion in a similar fashion to the modern depiction. The Hunter held an unidentified animal skin aloft in his right hand; his hand was represented byOmicron2 Orionis and the skin was represented by the five stars designatedPi Orionis.Saiph andRigel represented his left and right knees, whileEta Orionis andLambda Leporis were his left and right feet, respectively. As in the modern depiction,Mintaka,Alnilam, andAlnitak represented his Belt. His left shoulder was represented byBetelgeuse, andMu Orionis made up his left arm.Meissa was his head, andBellatrix his right shoulder. The depiction ofHyginus was similar to that of Cicero, though the two differed in a few important areas. Cicero's animal skin became Hyginus's shield (Omicron andPi Orionis), and instead of an arm marked out byMu Orionis, he holds a club (Chi Orionis). His right leg is represented byTheta Orionis and his left leg is represented by Lambda,Mu, andEpsilon Leporis. FurtherWestern European andArabic depictions have followed these two models.[43]
Future
Animation showing Orion's proper motion from 50000 BC to 50000 AD.Pi3 Orionis moves the most rapidly.
Orion is located on thecelestial equator, but it will not always be so located due to the effects ofprecession of theEarth's axis. Orion lies well south of theecliptic, 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 ofGemini andTaurus, to the north of Orion. Precession will eventually carry Orion further south, and by AD 14000, Orion will be far enough south that it will no longer be visible from the latitude ofGreat Britain.[64]
Further in the future,Orion's stars will gradually move away from the constellation due toproper motion. However, Orion's brightest stars all lie at a large distance fromEarth on an astronomical scale—much farther away thanSirius, for example. Orion will still be recognizable long after most of the otherconstellations—composed of relatively nearby stars—have distorted into new configurations, with the exception of a few of its stars eventually exploding assupernovae, for exampleBetelgeuse, which is predicted to explode sometime in the next million years.[65]
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