Auriga is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Located north of the celestial equator, its name is the Latin word for "charioteer", associating it with various mythological charioteers including Erichthonius and Myrtilus. Auriga is most prominent during winter evenings in the Northern Hemisphere, along with the five other constellations that have stars in the Winter Hexagon asterism. Because of its northern declination, Auriga is only visible as far as 34° south; for observers farther south it lies partially or fully below the horizon. A large constellation, with an area of 657 square degrees, it is half the size of the largest constellation, Hydra.
Its brightest star, Capella, is an unusual multiple star system among the brightest stars in the night sky. Beta Aurigae is an interesting variable star in the constellation; Epsilon Aurigae, a nearby eclipsing binary with an unusually long period, has been studied intensively. Because of its position near the winter Milky Way, Auriga has many bright open clusters in its borders, including M36, M37, and M38, popular targets for amateur astronomers. In addition, it has one prominentnebula, the Flaming Star Nebula, associated with the variable star AE Aurigae.
In Chinese mythology, Auriga's stars were incorporated into several constellations, including the celestial emperors' chariots, made up of the modern constellation's brightest stars. Auriga is home to the radiant for the Aurigids, Zeta Aurigids,Delta Aurigids, and the hypothesized Iota Aurigids.
History and mythology
The first record of Auriga's stars was in Mesopotamia as a constellation called GAM, representing a scimitar or crook. However, this may have represented just Capella (Alpha Aurigae) or the modern constellation as a whole; this figure was alternatively called Gamlum or MUL.GAM in the MUL.APIN. The crook of Auriga stood for a goat-herd or shepherd. It was formed from most of the stars of the modern constellation; all of the bright stars were included except for Elnath, traditionally assigned to both Taurus and Auriga. Later, Bedouin astronomers created constellations that were groups of animals, where each star represented one animal. The stars of Auriga comprised a herd of goats, an association also present in Greek mythology.[7] The association with goats carried into the Greek astronomical tradition, though it later became associated with a charioteer along with the shepherd.[8]
In Greek mythology, Auriga is often identified as the mythological Greek hero Erichthonius of Athens, the chthonic son of Hephaestus who was raised by the goddess Athena. Erichthonius was generally credited to be the inventor of the quadriga, the four-horse chariot, which he used in the battle against the usurper Amphictyon, the event that made Erichthonius the king of Athens.[9][10]His chariot was created in the image of the Sun's chariot, the reason Zeus placed him in the heavens.[11] The Athenian hero then dedicated himself to Athena and soon after, Zeus raised him into the night sky in honor of his ingenuity and heroic deeds.[12]
Auriga, however, is sometimes named as Myrtilus, who was Hermes's son and the charioteer of Oenomaus.[10] The association of Auriga and Myrtilus is supported by depictions of the constellation, which rarely show a chariot. Myrtilus's chariot was destroyed in a race intended for suitors to win the heart of Oenomaus's daughter Hippodamia. Myrtilus earned his position in the sky when Hippodamia's successful suitor, Pelops, killed him, despite his complicity in helping Pelops win her hand. After his death, Myrtilus's father Hermes placed him in the sky. Yet another mythological association of Auriga is Theseus's son Hippolytus. He was ejected from Athens after he refused the romantic advances of his stepmother Phaedra, who committed suicide as a result. He was killed when his chariot was wrecked, but revived by Asclepius.[11][13] Regardless of Auriga's specific representation, it is likely that the constellation was created by the ancient Greeks to commemorate the importance of the chariot in their society.[14]
An incidental appearance of Auriga in Greek mythology is as the limbs of Medea's brother. In the myth of Jason and the Argonauts, as they journeyed home, Medea killed her brother and dismembered him, flinging the parts of his body into the sea, represented by the Milky Way. Each individual star represents a different limb.[15]
Capella is associated with the mythological she-goat Amalthea, who breast-fed the infant Zeus. It forms an asterism with the stars Epsilon Aurigae, Zeta Aurigae, and Eta Aurigae, the latter two of which are known as the Haedi (the Kids).[9][16] Though most often associated with Amalthea, Capella has sometimes been associated with Amalthea's owner, a nymph. The myth of the nymph says that the goat's hideous appearance, resembling a Gorgon, was partially responsible for the Titans' defeat, because Zeus skinned the goat and wore it as his aegis.[11] The asterism containing the three goats had been a separate constellation; however, Ptolemy merged the Charioteer and the Goats in the 2nd century Almagest.[14] Before Ptolemy's merge, Capella was sometimes seen as its own constellation—by Pliny the Elder and Manilius—called Capra, Caper, or Hircus, all of which relate to its status as the "goat star".[17] Zeta Aurigae and Eta Aurigae were first called the "Kids" by Cleostratus, an ancient Greek astronomer.[11]
Traditionally, illustrations of Auriga represent it as a chariot and its driver. The charioteer holds a goat over his left shoulder and has two kids under his left arm; he holds the reins to the chariot in his right hand.[2] However, depictions of Auriga have been inconsistent over the years. The reins in his right hand have also been drawn as a whip, though Capella is almost always over his left shoulder and the Kids under his left arm. The 1488 atlas Hyginus deviated from this typical depiction by showing a four-wheeled cart driven by Auriga, who holds the reins of two oxen, a horse, and a zebra. Jacob Micyllus depicted Auriga in his Hyginus of 1535 as a charioteer with a two-wheeled cart, powered by two horses and two oxen. Arabic and Turkish depictions of Auriga varied wildly from those of the European Renaissance; one Turkish atlas depicted the stars of Auriga as a mule, called Mulus clitellatus by Johann Bayer.[17] One unusual representation of Auriga, from 17th-century France, showed Auriga as Adam kneeling on the Milky Way, with a goat wrapped around his shoulders.[18]
Occasionally, Auriga is seen not as the Charioteer but as Bellerophon, the mortal rider of Pegasus who dared to approach Mount Olympus. In this version of the tale, Jupiter pitied Bellerophon for his foolishness and placed him in the stars.[19]
Some of the stars of Auriga were incorporated into a now-defunct constellation called Telescopium Herschelii. This constellation was introduced by Maximilian Hell to honor William Herschel's discovery of Uranus. Originally, it included two constellations, Tubus Hershelii Major [sic], in Gemini, Lynx, and Auriga, and Tubus Hershelii Minor [sic] in Orion and Taurus; both represented Herschel's telescopes. Johann Bode combined Hell's constellations into Telescopium Herschelii in 1801, located mostly in Auriga.[20]
Since the time of Ptolemy, Auriga has remained a constellation and is officially recognized by the International Astronomical Union, although like all modern constellations, it is now defined as a specific region of the sky that includes both the ancient pattern and the surrounding stars.[21][22] In 1922, the IAU designated its recommended three-letter abbreviation, "Aur".[23] The official boundaries of Auriga were created in 1930 by Eugène Delporte as a polygon of 21 segments. Its right ascension is between 4h 37.5m and 7h 30.5m and its declination is between 27.9° and 56.2° in the equatorial coordinate system.[24]
In non-Western astronomy
The stars of Auriga were incorporated into several Chinese constellations. Wuche, the five chariots of the celestial emperors and the representation of the grain harvest, was a constellation formed by Alpha Aurigae, Beta Aurigae, Beta Tauri, Theta Aurigae, and Iota Aurigae. Sanzhu or Zhu was one of three constellations which represented poles for horses to be tethered. They were formed by the triplets of Epsilon, Zeta, and Eta Aurigae; Nu, Tau, and Upsilon Aurigae; and Chi and 26 Aurigae, with one other undetermined star. Xianchi, the pond where the sun set and Tianhuang, a pond, bridge, or pier, were other constellations in Auriga, though the stars that composed them are undetermined. Zuoqi, representing chairs for the emperor and other officials, was made up of nine stars in the east of the constellation. Bagu, a constellation mostly formed from stars in Camelopardalis representing different types of crops, included the northern stars of Delta and Xi Aurigae.[11]
In ancient Hindu astronomy, Capella represented the heart of Brahma and was important religiously. Ancient Peruvian peoples saw Capella, called Colca, as a star intimately connected to the affairs of shepherds.[18]
In Brazil, the Bororo people incorporate the stars of Auriga into a massive constellation representing a caiman; its southern stars represent the end of the animal's tail. The eastern portion of Taurus is the rest of the tail, while Orion is its body and Lepus is the head. This constellation arose because of the prominence of caymans in daily Amazonian life.[25] There is evidence that Capella was significant to the Aztec people, as the Late Classic site Monte Albán has a marker for the star's heliacal rising.[26] Indigenous peoples of California and Nevada also noticed the bright pattern of Auriga's stars. To them, the constellation's bright stars formed a curve that was represented in crescent-shaped petroglyphs.[27] The indigenous Pawnee of North America recognized a constellation with the same major stars as modern Auriga: Alpha, Beta, Gamma (Beta Tauri), Theta, and Iota Aurigae.[28]
The people of the Marshall Islands featured Auriga in the myth of Dümur, which tells the story of the creation of the sky. Antares in Scorpius represents Dümur, the oldest son of the stars' mother, and the Pleiades represent her youngest son. The mother of the stars, Ligedaner,[29][30] is represented by Capella; she lived on the island of Alinablab. She told her sons that the first to reach an eastern island would become the King of the Stars, and asked Dümur to let her come in his canoe. He refused, as did each of her sons in turn, except for Pleiades. Pleiades won the race with the help of Ligedaner, and became the King of the Stars.[29] Elsewhere in the central Caroline Islands, Capella was called Jefegen uun (variations include efang alul, evang-el-ul, and iefangel uul), meaning "north of Aldebaran".[31] Different names were noted for Auriga and Capella in Eastern Pacific societies. On Pukapuka, the figure of modern Auriga was called Te Wale-o-Tutakaiolo ("The house of Tutakaiolo");[32] in the Society Islands, it was called Faa-nui ("Great Valley").[33] Capella itself was called Tahi-anii ("Unique Sovereign") in the Societies.[34] Hoku-lei was the name for Capella but may have been the name for the whole constellation; the name means "Star-wreath" and refers to one of the wives of the Pleiades, called Makalii.[35]
The stars of Auriga feature in Inuit constellations. Quturjuuk, meaning "collar-bones",[36] was a constellation that included Capella (Alpha Aurigae), Menkalinan (Beta Aurigae), Pollux (Beta Geminorum), and Castor (Alpha Geminorum). Its rising signalled that the constellation Aagjuuk, made up of Altair (Alpha Aquilae), Tarazed (Gamma Aquilae), and sometimes Alshain (Beta Aquilae), would rise soon. Aagjuuk, which represented the dawn following the winter solstice, was an incredibly important constellation in the Inuit mythos.[37] It was also used for navigation and time-keeping at night.[38]
Notable features
Stars
Bright stars
Alpha Aurigae (Capella), the brightest star in Auriga, is a G8III class star (G-type giant) 43 light-years away[39] and the sixth brightest star in the night sky at magnitude 0.08.[9] Its traditional name is a reference to its mythological position as Amalthea; it is sometimes called the "Goat Star".[2][16][40] Capella's names all point to this mythology. In Arabic, Capella was called al-'Ayyuq, meaning "the goat", and in Sumerian, it was called mul.ÁŠ.KAR, "the goat star".[41] On Ontong Java, Capella was called ngahalapolu.[42] Capella is a spectroscopic binary with a period of 104 days; the components are both yellow giants,[16] more specifically, the primary is a G-type star and the secondary is between a G-type and F-type star in its evolution.[43] The secondary is formally classified as a G0III class star (G-type giant).[39] The primary has a radius of 11.87 solar radii (R☉) and a mass of 2.47 solar masses (M☉); the secondary has a radius of 8.75 R☉ and a mass of 2.44 M☉. The two components are separated by 110 million kilometers, almost 75% of the distance between the Earth and the Sun.[44] The star's status as a binary was discovered in 1899 at theLick Observatory; its period was determined in 1919 by J.A. Anderson at the 100-inch Mt. Wilson Observatory telescope. It appears with a golden-yellow hue, though Ptolemy and Giovanni Battista Riccioli both described its color as red, a phenomenon attributed not to a change in Capella's color but to the idiosyncrasies of their color sensitivities.[40] Capella has an absolute magnitude of 0.3 and a luminosity of 160 times the luminosity of the Sun, or 160 L☉ (the primary is 90 L☉ and the secondary is 70 L☉).[43] It may be loosely associated with the Hyades, an open cluster in Taurus, because of their similar proper motion. Capella has one more companion, Capella H, which is a pair of red dwarf stars located 11,000 astronomical units (0.17 light-years) from the main pair.[40]
Beta Aurigae (Menkalinan, Menkarlina)[16] is a bright A2IV class star (A-type subgiant).[9][45] Its Arabic name comes from the phrase mankib dhu al-'inan, meaning "shoulder of the charioteer" and is a reference to Beta Aurigae's location in the constellation.[41] Menkalinan is 81 light-years away[45] and has a magnitude of 1.90. Like Epsilon Aurigae, it is an eclipsing binary star that varies in magnitude by 0.1m. The two components are blue-white stars that have a period of 3.96 days.[16] Its double nature was revealed spectroscopically in 1890 by Antonia Maury,[40] making it the second spectroscopic binary discovered,[46] and its variable nature was discovered photometrically 20 years later by Joel Stebbins.[40] Menkalinan has an absolute magnitude of 0.6 and a luminosity of 50 L☉.[43] The component of its motion in the direction of Earth is 18 kilometres (11 mi) per second. Beta Aurigae may be associated with a stream of abount 70 stars including Delta Leonis and Alpha Ophiuchi; the proper motion of this group is comparable to that of the Ursa Major Moving Group, though the connection is only hypothesized. Besides its close eclipsing companion, Menkalinan has two other stars associated with it. One is an unrelated optical companion, discovered in 1783 by William Herschel; it has a magnitude of 10.5 and has a separation of 184 arcseconds. The other is likely associated gravitationally with the primary, as determined by their common proper motion. This 14th magnitude star was discovered in 1901 by Edward Emerson Barnard. It has a separation of 12.6 arcseconds, and is around 350 astronomical units from the primary.[40]
Other bright stars
Besides the particularly bright stars of Alpha and Beta Aurigae, the constellation has many dimmer stars. Gamma Aurigae, now Beta Tauri (El Nath, Alnath) is a B7III class star (B-type giant).[47] It was originally considered to be a part of both Auriga and Taurus, but is now classified only as Beta Tauri.[9][16] Iota Aurigae, also called Hasseleh and Kabdhilinan, is a K3II class star (K-type bright giant)[48] of magnitude 2.69;[9][43] it is 494 light-years away from Earth.[48]It evolved from a B-type star to a K-type star over the estimated 30–45 million years since its birth.[49] Iota Aurigae has an absolute magnitude of −2.3 and a luminosity of 700 L☉.[43] It is classed as a particularly luminous bright giant, but appears dimmer than it should because dust clouds in the Milky Way block some of its light; astronomers estimate that it appears 0.6 magnitudes fainter.[49] It is also a hybrid star, an x-ray producing giant star that emits x-rays from its corona and has a cool stellar wind.[49][50] Though its proper motion is just 0.02 arcseconds per year, it has a radial velocity of 10.5 miles (16.9 km) per second in recession.[40] The traditional name Kabdhilinan, sometimes shortened to "Alkab", comes from the Arabic phrase al-kab dh'il inan, meaning "shoulder of the rein holder". Iota Aurigae may end as a supernova, but because it is close to the mass limit for such stars, it may instead become a white dwarf.[49]
Delta Aurigae, the northernmost bright star in Auriga,[51] is a K0III-type star (K-type giant),[43][51][52] 126 light-years from Earth[52] and approximately 1.3 billion years old.[51] It has a magnitude of 3.72, an absolute magnitude of 0.2, and a luminosity of 60 L☉.[43] About 12 times the radius of the Sun, Delta Aurigae weighs only two solar masses and rotates with a period of almost one year.[51] Though it is often listed as a single star,[53] it actually has three very widely spaced optical companions. One is a double star of magnitude 11, two arcminutes from Delta, and the other is a star of magnitude 10, three arcminutes from Delta.[51]
Lambda Aurigae (Al Hurr)[2] is a G1.5IV-V-type star (G-type star intermediate between a subgiant and main-sequence star)[54] of magnitude 4.71. It has an absolute magnitude of 4.4[43] and is located 41 light-years from Earth.[54] It has very weak emissions in the infrared spectrum, like Epsilon Aurigae.[55] In photometric observations of Epsilon, an unusual variable, Lambda Aurigae is commonly used as a comparison star.[56][57] It is reaching the end of its hydrogen-fusing lifespan at an age of 6.2 billion years. It also has an unusually high radial velocity at 83 km/second. Though older than the Sun, it is similar in many ways; its mass is 1.07 solar masses, a radius of 1.3 solar radii, and a rotational period of 26 days. However, it differs from the Sun in its metallicity; its iron content is 1.15 times that of the Sun and it has relatively less nitrogen and carbon. Like Delta, it has several optical companions and is often categorized as a single star. The brightest companions are of magnitude 10, separated by 175 and 203 arcseconds. The dimmer companions are of magnitude 13 and 14, 87 and 310 arcseconds from Lambda, respectively.[58] Nu Aurigaeis a G9.5III (G-type giant)[59] star of magnitude 3.97,[43] 230 light-years from Earth.[59] It has a luminosity of 60L☉ and an absolute magnitude of 0.2.[43] Nu Aurigae is a giant star with a radius of 20–21 solar radii and a mass of approximately 3 solar masses. It may technically be a binary star; its companion, sometimes listed as optical and separated by 56 arcseconds, is a dwarf star of spectral type K6 and magnitude 11.4. Its period is more than 120,000 years and it orbits at least 3700 AU from the primary.[51]
| Star | Spectral class | Apparent magnitude[43] | Absolute magnitude[43] | Distance (light-years) |
|---|---|---|---|---|
| Tau Aurigae | G8III[60] | 4.52 | 0.3 | 206[60] |
| Upsilon Aurigae | M0III[61] | 4.74 | −0.5 | 526[61] |
| Pi Aurigae | M3II[62] | 4.26 | −2.4 | 758[62] |
| Kappa Aurigae | G8.5IIIb[63] | 4.25 | 0.3 | 177[63] |
| Omega Aurigae | A1V[64] | 4.94 | 0.6 | 171[64] |
| 2 Aurigae | K3III[65] | 4.78 | −0.2 | 604[65] |
| 9 Aurigae | F0V[66] | 5.00 | 2.6 | 86[66] |
| Mu Aurigae | A4m[67] | 4.86 | 1.8 | 153[67] |
| Sigma Aurigae | K4III[68] | 4.89 | −0.3 | 466[68] |
| Chi Aurigae | B4Ib[69] | 4.76 | −6.3 | 3032[43] |
| Xi Aurigae | A2V[70] | 4.99 | 0.8 | 233[70]
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