Constellations: Auriga 'the Charioteer' Content from the guide to life, the universe and everything

Constellations: Auriga 'the Charioteer'

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The shield of the Science, Mathematics and Engineering faculty of the h2g2 University.Constellations: Overview | Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Boötes | Caelum
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The constellation Auriga.
Name:Auriga (Latin: 'charioteer')
Short form:Aur
Area:657 sq deg
Co-ordinates:Right Ascension 06h, Declination +40°

The northern constellation of Auriga the Charioteer is best seen in the winter months in the northern hemisphere and is one of the 48 constellations listed by Ptolemy in the Almagest. It is a prominent constellation covering a large area which includes the sixth brightest star in the night sky, the 1st magnitude  Capella. During winter evenings Auriga is located almost overhead, and Capella's yellow hue marks it out. The adjacent constellations of Gemini and Taurus are to its south-east and south-west, separating it from the mighty Orion which is directly to its south.

With Capella, six prominent stars of 2nd and 3rd magnitude make up the roughly rhomboid shape of the constellation. The Milky Way passes directly through Auriga; consequently it contains some fine star clusters, three of which have been graced with Messier numbers.

Mythology and History

Alternatively known as the Herdsman or the Wagoner, the myth originates from Babylonian lore. It depicts a young man with a whip in his right hand, a goat across his left arm and shoulder, and a pair of goat kids at his left hand. There is, however, no sign of a chariot until represented in the translation of the works of Hyginus, the Greek historian of the last Century BC.

From classical mythology the figure is said to represent Erichthonius, the son of Vulcan and Minerva, who, because he was lame, was banished to Earth. He was the blacksmith to the gods, and later became the king of Athens. He is said to have created the four-horse chariot to carry him in a manner befitting his position when he became monarch.

A small triangle asterism within Auriga is Haidi or the Kids, named by Pliny, the Roman naturalist. To assist ancient mariners in the Mediterranean region, Pliny declared that its appearance in the early October evenings presaged the onset of bad weather and advised the closing of sea-going navigation for its duration. A great festival, the Natalis navigationis was held later each year to mark the end of its influence.

Principal Stars

The constellation's alpha star Capella ('little she-goat'), is named from classical times and represents the goat carried by the wagoner on his left arm. In astrology it signifies wealth and honour. It shines with a definite yellow hue and is the most northerly of the 1st magnitude stars. It is 42 light years1 distant and spectroscopic analysis shows it to be similar in its physical attributes to our own Sun. It is, however, some 70 times more luminous. It is a close binary system and comprises two G-class stars orbiting each other in a period of 104 days. This pair is orbited by another pair of M-class red dwarfs at a distance of one light year.

Beta Aurigae, Menkalinan, is another spectroscopic binary and its unseen companion eclipses the primary star every 89 hours. Its actual brightness is some 110 times that of our Sun, although to us it shines at a 2nd degree magnitude. The name means 'shoulder of the rein holder' signifying its position in the constellation.

There is no longer a 'gamma Aurigae'. The rhomboid-shaped star grouping's southern point was, and still is, marked by beta Tauri, Al Nath. This star was designated 'gamma Aurigae' until the IAU2 formalised the boundaries of the individual constellations and allocated Al Nath to the constellation of Taurus the Bull.

Delta Aurigae lies to the north and denotes the head of the charioteer. Somewhat surprisingly it does not seem to have been named, perhaps because it is rather inconspicuous.

Epsilon Aurigae, Al Ma'az, is the 'he goat' on the arm of the charioteer, lying at over 2,000 light years distance. It is another binary system, eclipsing every 27 years, taking 190 days to drop from its normal +2.99 magnitude to +3.8 and return. The next variation is due in 2036.

Zeta Aurigae, together with eta and epsilon, form a tight triangle asterism3 at the waist of the figure. They are named collectively the Haedi or the Kids and represent the two young goats at the charioteer's hand.

Star Table

StarDesignationNameBrightness (m)Distance (light years)Remarks
α Auralpha AurigaeCapella+0.0842Spectroscopic double
β Aurbeta AurigaeMenkalinan+1.9072Spectroscopic binary
δ Aurdelta Aurigae33 Aurigae+4.1140.6Spectroscopic double
ε Aurepsilon AurigaeAl Ma'az+2.992,000Eclipsing binary
ζ Aurzeta AurigaeSadatoni+3.75360Haedi (The Kids)
η Aureta Aurigae10 Aurigae+3.20310Blue-white dwarf

Star Clusters and Nebulae

An arm of the Milky Way runs through Auriga; consequently star clusters abound within this constellation. Charles Messier listed the three most prominent in his famous catalogue of 'non-comets'. M36, M37 and M38 are directly south of Capella and near to beta Tauri. M36 and M38 were discovered by the French astronomer Guillaume Le Gentil (1725 - 92), while M37 was discovered by Messier himself. All three Messier objects are easily seen with binoculars.

M36 is an open cluster of approximately 60 stars spanning an angular width of 12 arc minutes. All the stars in the cluster are young, and combined show at 6th magnitude. M37 contains about 150 stars spread further across 20 arc minutes and is apparently slightly brighter at magnitude +5.6. M38 consists of a group of about 100 stars and is the dimmest of the three Messier clusters at magnitude +6.4. NGC 1931 is an open cluster with an overall magnitude of +5.4 and NGC 1907 at +8.2 magnitude is just south of M38. All in all, Auriga is a rewarding constellation to browse with binoculars for the rich star clusters which are easily found.

In December 1891, the Reverend Doctor Thomas Anderson, an amateur observer using a pair of opera glasses4, found a new star in Auriga. In fact he had spotted a nova which brightened to a magnitude +4.4 and eventually dimmed to become invisible to the naked eye by April 1892. It was later found to have been recorded on photographs taken at the Mount Hamilton Observatory, but had been missed. By August it had become a planetary nebula, and was visible by long exposure photography. This was only the second time that the progression from nova to nebula had been recorded.

Unfortunately, not likely to be seen with binoculars is IC 405, otherwise known as the 'Flaming Star Nebula'. A small telescope is required to view the five-light-year-wide cloud of gas and dust that comprises the nebula. The very hot, blue/white star AE Aurigae in its centre emits light that results from electrons being stripped away from the gaseous atoms. Protons, recapturing these free electrons, emit a red light creating an emission nebula with an overall red hue. Where this light mixes with the star's blue/white light and is reflected from the surrounding dust, it creates a violet/purple-coloured reflection nebula surrounding the star. AE Aurigae is a 'runaway star', believed to have been created within the Orion Nebula only two million years ago, and is now passing through, or behind IC 405.

Star Clusters and Nebulae

CatalogueTypeBrightness (m)Distance (light years)Remarks
M36Open cluster+6.04,100NGC 1960
M37Open cluster+5.64,400NGC 2099
M38Open cluster+6.44,200NGC 1912
NGC 1931Open cluster with nebulosity+5.410,000approx 30 stars
NGC 1907Open cluster+8.24,50030-35 stars
IC 405Emission/Reflection Nebula+5.91,500Flaming Star Nebula

Meteor Showers

Auriga hosts at least four meteor showers through the course of the year, all of which have a low hourly rate. The prime shower, the Aurigids, occur between the end of January and late February with the maximum of 18 per hour between 9 and 17 February. At the start of the 20th Century the shower was producing some significant fireballs of spectacular proportions, but has currently reduced to an average of less than one per hour.

The Alpha Aurigids occur between 25 August and 6 September, with the maximum around 1 September, although they do not appear every year. The radiant5 in this case appears to be near Capella, and has been attributed to the debris trail left by Comet Keiss when it passed through the solar system in 1911.

The Delta Aurigids appear between September and October and have a maximum occurring near 8 October. Their radiant is delta Aurigae and their source appears to be from Comet Bradfield, discovered in 1972.

The Zeta Aurigids is a minor shower occurring between 11 December and 21 January reaching maximum around 31 December. For the most part this shower is observable only by radar and appears to be a split shower with a northern and a southern stream. Occasional fireballs appear in the northern stream.

Extrasolar Planets

There are many stars with orbiting planets within the limits of Auriga. Stars designated HD 40979, HD 43691, HD 45350 and HD 49674 are all unnamed. Three of those planets (all catalogued 'b') are gas giants with masses between two and four times that of our own solar system's largest planet Jupiter. Only one, HD 49674 b bucks the usual trend and is approximately 1/10th that of Jupiter; however it is still a 'gas giant'. HAT-P-9 b orbits so hellishly close to its star, its 'year' is completed in four Earth days. The Hubble Space Telescope has seen the planet WASP-12 b which takes just over one Earth day to orbit its parent star! In 2012 a hot Jupiter named KELT-2A b was discovered in a binary system.

Charioteering Through the Ages

One famous charioteer was Pharaoh Tutankhamun, the 'boy king'. We know this because several chariots were found in his tomb, including one complete golden one, which now resides in the Egyptian Museum in Cairo. Clothing found in his tomb was demonstrated on a model in a TV documentary to show how his inner organs would have been protected in the event of an accident while driving fast. Such speeds were only possible by horse-power over 3,300 years ago, and one-man chariots were used for hunting and racing. Pharaoh Tutankhamun would also have had a two-seater for himself and his wife, with his own personal driver. There are some people today, including the Secretary General of the Egyptian Supreme Council of Antiquities Dr Zahi Hawass, who believe that Tutankhamun met his early death following a chariot-racing or hunting accident rather than the murder conspiracy theories.

In Roman times wealthy and influential individuals would employ a trusted slave to drive the family chariot. This early version of the chauffeur was known as an 'Auriga'. It is thought that one of the duties of the Auriga during triumphal processions was to hold a laurel crown over the head of the fêted one and to continually whisper in his ear Memento homo6. The intent was to prevent the adulation from inflating the ego of the adored one further than it already was.

Another figure from history credited with expertise in chariot driving is the Iceni Queen Boudicca. Said to have addressed her troops from a chariot on the eve of her last battle against the Romans, her defiance in the face of the Roman Empire is commemorated by a prominent statue at the northern end of Westminster Bridge, London, in the shadow of the Houses of Parliament. Sculpted by artist Thomas Thornycroft, it portrays Boudicca and her daughters in a chariot drawn by two wild-eyed horses.

In 1880 author Lew Wallace published a story which features a hero who becomes a champion charioteer. During the 20th Century three films were made from the book, each one featuring the brutality of the chariot race in classical Roman times. The hero is Judah Ben Hur, and all three films were titled Ben Hur. Driving a quadriga of four white Arabian horses, our hero prevails against his adversary. The horses are owned by Judean Sheikh Ilderim, who has named them Rigel, Antares, Altair and Aldebaran after prominent stars. These names would not, however, have been available to a sheikh of the 1st Century AD.

A chariot race of a different ilk occurs in the 1999 'Star Wars' film, The Phantom Menace. Many of the racing pods are pulled by their multiple power units, which are connected to the occupied pod only by a cable, giving the impression of a horse and chariot. Similarities have been noted between the pod race and the chariot race in Ben Hur: the storyline of the race, the good/evil protagonists, their tactics and, if the imagination is stretched a little, even facial similarities between Sheikh Ilderim, played by actor Hugh Griffith, and Watto, the 'good' team race sponsor.

The fourth film in the 'Alien' series, Alien Resurrection, takes place on the spacecraft USM Auriga. After a number of unsuccessful attempts, Ellen Ripley (Sigourney Weaver) has been cloned into existence in order to harvest the parasitic alien creature. The usual mayhem ensues.

1A 'light year' is the distance light travels in one year, roughly 5.88 trillion miles or 9.46 trillion km.2IAU stands for International Astronomical Union.3A group of stars which isn't a recognised constellation.4Inexpensive pre-focused binoculars. Usually found on the back of seats in theatres for the use of patrons seated 'up in the gods'.5The point at which the meteors appear to originate from when their tracks are traced back to the position where they intersect.6Literally translated to 'Remember, you are only a man'.

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