Auriga constellation lies in the northern hemisphere. Its name means ‘the charioteer’ in Latin. Auriga is the 21st biggest constellation in the night sky, occupying 657 square degrees. It is located in the first quadrant of the northern hemisphere (NQ1) and can be seen at latitudes between +90° and -40°. The neighboring constellations are Camelopardalis, Gemini, Lynx, Perseus, and Taurus. Auriga belongs to the Perseus family of constellations, together with Andromeda, Cassiopeia, Cepheus, Cetus, Lacerta, Pegasus, Perseus, and Triangulum. The constellation is also the site of the galactic anti-centre, the point in the sky opposite to the centre of the Milky Way Galaxy, which is located in the constellation Sagittarius, near the border with Scorpius. The nearest bright star to the galactic anti-centre is Alnath, Beta Tauri.
[http://www.constellation-guide.com/constellation-list/auriga-constellation/]
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 in its entirety 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.
Auriga carrying the goat and kids, seen on Chart V of the Uranographia of Johann Bode (1801). The bright star Capella lies in the body of the goat.
[http://www.ianridpath.com/startales/auriga.htm]
Traditionally, illustrations of Auriga represent it as a chariot and its driver. The charioteer holds a goat (Capella, Alpha Aurigae) over his left shoulder and has two kids (Zeta Aurigae, and Eta Aurigae) under his left arm; he holds the reins to the chariot in his right hand. However, depictions of Auriga have been inconsistent over the years.
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. The association with goats carried into the Greek astronomical tradition, though it later became associated with a charioteer along with the shepherd.
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. His chariot was created in the image of the Sun’s chariot, the reason Zeus placed him in the heavens. 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.
Auriga, however, is sometimes described as Myrtilus, who was Hermes’s son and the charioteer of Oenomaus. 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.
In Chinese 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.
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. 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. 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. 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. 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.
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, 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. 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.’ 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’); in the Society Islands, it was called Faa-nui (‘Great Valley’). Capella itself was called Tahi-anii (‘Unique Sovereign’) in the Societies. 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.
The stars of Auriga also feature in Inuit constellations. Quturjuuk, meaning ‘collar-bones,’ was a constellation that included Capella (Alpha Aurigae), Menkalinan (Beta Aurigae), Pollux (Beta Geminorum), and Castor (Alpha Geminorum). Its rising signaled 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. It was also used for navigation and time-keeping at night.
An image of the constellations Auriga and Taurus.
[http://oneminuteastronomer.com/3295/constellation-auriga/]
[http://astropixels.com/constellations/charts/Aur.html]
A size comparison of the four stars in the Capella system and the Sun
Capella is the brightest star in the constellation Auriga, the sixth brightest in the night sky and the third brightest in the northern celestial hemisphere, after Arcturus and Vega. Its name is derived from the diminutive of the Latin feminine capra ‘goat,’ hence ‘little she goat.’ This symbolism dates back to Mesopotamia as a constellation called GAM, representing a scimitar or crook. It traditionally marks the left shoulder of the constellation’s eponymous charioteer, or, according to Ptolemy, the goat that the charioteer is carrying. In Greek mythology, the star represented the goat Amalthea that suckled Zeus, or Amalthea’s owner, a nymph. Capella forms an asterism with the stars Epsilon, Zeta, and Eta Aurigae, the latter two of which are known as the Haedi (the Kids).
Although Capella appears to be a single star to the naked eye, it is actually a star system of four stars in two binary pairs. The first pair consists of two bright, type-G giant stars, designated Capella Aa and Capella Ab, in a very tight circular orbit some 0.76 AU apart and a derived orbital period of 104 days. Capella Aa is the brighter of the two at spectral class G8III (G8 Giant) whereas Ab is slightly smaller and of spectral class G0III (G0 Giant). Aa has a calculated mass of 3.05 times that of the Sun and Ab some 2.57 times that of the Sun. These two stars have both exhausted their core hydrogen fuel and become giant stars, though it is unclear exactly what stage they are on the stellar evolutionary pathway.
The second pair, around 10,000 astronomical units from the first, consists of two faint, small and relatively cool red dwarfs. They are designated Capella H and Capella L. The stars labelled Capella C through to G and I through to K are actually unrelated stars in the same visual field.
The Capella system is relatively close, at only 42.8 light-years (13.1 pc) from Earth.
[https://en.wikipedia.org/wiki/Capella]
Beta Aurigae has the traditional name Menkalinan, from the Arabic ‘mankib ðī-l-‘inān,’ ‘shoulder of the rein-holder.’ It is a binary system, with a combined apparent visual magnitude of 1.9, making it the second brightest member of the constellation after Capella. The distance to this star system is 81.1 light-years (24.9 parsecs).
The two brightest components are metallic-lined subgiant stars belonging to the A-type stellar classification; they have roughly the same mass and radius. A-type entities are hot stars that release a blue-white hued light; these two stars burn brighter and with more heat than the Sun, which is a G2-type main sequence star. The pair constitute an eclipsing spectroscopic binary; the combined apparent magnitude varies over a period of 3.96 days between +1.89 and +1.94, as every 47.5 hours one of the stars partially eclipses the other from Earth’s perspective.
At an angular separation of 13.9 ± 0.3 arcseconds along a position angle of 155° is a companion star that is 8.5 magnitudes fainter than the binary pair. This is a candidate member of Beta Aurigae, which would make it a triple (trinary) star system. It may be the source of the X-ray emission from the vicinity.
[https://en.wikipedia.org/wiki/Beta_Aurigae]
Theta Aurigae is sometimes called Mahasim, from the Arabic ‘wrist’ (of the charioteer), which was also used for Eta Aurigae. The distance to this star is about 166 light-years (51 parsecs). Theta Aurigae is a binary star. The primary component is a large star with more than three times the mass of the Sun and over five times the Sun’s radius. It is radiating 263 times the Sun’s luminosity from its outer atmosphere at an effective temperature of 10,400 K, giving it the white hue of an A-type star. The star has a stellar classification of A0pSi, with the ‘pSi’ suffix indicating it is a chemically peculiar star with an abnormal abundance of silicon.
There is a +7.2 magnitude companion, 4.5 magnitudes fainter than the primary, located at an angular separation of 3.91 arcseconds along a position angle of 304.9° as of 2002. This is an F-type main sequence star with a stellar classification in the range F2-5 V. The mean combined apparent magnitude of the system is +2.65 but the variation of the primary causes the system’s brightness ranges from magnitude +2.62 to +2.70 with a period of 1.37 days. The system is an X-ray source with a luminosity of 9.49 × 1026 erg s−1.
[https://en.wikipedia.org/wiki/Theta_Aurigae]
Iota Aurigae has the traditional name AlKab, short for Kabdhilinan, from the Arabic ‘al-kacb ðīl-cinān,’ ‘the shoulder of the rein holder (charioteer).’ This star has an apparent visual magnitude of 2.7, which is bright enough to be readily visible to the naked eye. It is roughly 490 light-years (150 parsecs) distant from the Earth. Examination of the spectrum yields a stellar classification of K3 II, with the luminosity class of ‘II’ indicating this is a category of evolved star known as a bright giant. The effective temperature of the outer envelope is 4,160 K, which is cooler than the Sun’s effective temperature and gives Iota Aurigae the orange hue of a K-type star.
[https://en.wikipedia.org/wiki/Iota_Aurigae]
New pictures confirm that a dark disk is responsible for the star Epsilon Aurigae’s regular, 18-month-long eclipses.
[http://www.universetoday.com/49443/epsilon-aurigae-eclipse-mystery-solved-with-your-help/]
Epsilon Aurigae star system (artist impression)
Epsilon Aurigae is also known colloquially as Almaaz, Haldus or Al Anz. Both Almaaz and Al Anz derive from the Arabic ‘al-mācz,’ ‘(billy) goat,’ corresponding to the name of the star Capella (Latin for ‘nanny goat’). Epsilon Aurigae is an unusual eclipsing binary system comprising an F0 supergiant and a companion which is generally accepted to be a huge dark disk orbiting an unknown object, possibly a binary system of two small B-type stars. About every 27 years, Epsilon Aurigae’s brightness drops from an apparent visual magnitude of +2.92 to +3.83. This dimming lasts 640–730 days. The star is easily found because of its brightness and apparent proximity to the star Capella. It is the apex of the isosceles triangle forming the ‘nose’ of the constellation Auriga. The star is bright enough to be seen from most urban locations with moderate amounts of light pollution. Visual variable star observers make an estimate of its brightness by comparing its brightness with nearby stars with a known brightness value. The distance to the system is still a subject of debate, but modern estimates place it approximately 2,000 light years from Earth.
The visible component, Epsilon Aurigae A, is a semiregular pulsating post-asymptotic giant branch star belonging to the spectral class F0. This F-type star has around 135 to 190 times the diameter of the Sun, and is 70,000 to 80,000 times as luminous. (Reliable sources vary considerably in their estimates of both quantities.) If the star were in the position of the Sun, it would envelop Mercury and possibly Venus. F-type stars like Epsilon Aurigae tend to glow white and display strong ionized calcium absorption lines and weak hydrogen absorption lines; being a class above the Sun (which is a G-type star), F-type stars are typically hotter than sunlike stars.
Epsilon Aurigae’s eclipsing companion has been subject to much debate since the object does not emit as much light as is expected for an object its size. As of 2008, the most popularly accepted model for this companion object is a binary star system surrounded by a massive, opaque disk of dust; theories speculating that the object is a large, semitransparent star or a black hole have since been discarded.
[https://en.wikipedia.org/wiki/Epsilon_Aurigae]
Another eclipsing binary in Auriga, part of the Haedi (the Kids) asterism with Epsilon Aurigae, is Zeta Aurigae (Haedus or Sadatoni), an eclipsing binary star at a distance of 776 light-years with a period of 2 years and 8 months. It has an absolute magnitude of −2.3. The primary is an orange-hued K5II-type star (K-type bright giant) and the secondary is a smaller blue star similar to Regulus; its period is 972 days. The secondary is a B7V-type star, a B-type main-sequence star. Zeta Aurigae’s maximum magnitude is 3.7 and its minimum magnitude is 4.0. The full eclipse of the small blue star by the orange giant lasts 38 days, with two partial phases of 32 days at the beginning and end. The primary has a radius of 150 solar radii and a luminosity 700 times that of the sun; the secondary has a radius of 4 solar radii and a luminosity of 140 times that of the sun.
The third star in the asterism of the Kids is Eta Aurigae (Haedus II), a B3 class star located 243 light-years from Earth with a magnitude of 3.17. It is a B3V class star, meaning that it is a blue-white hued main-sequence star. Eta Aurigae has an absolute magnitude of −1.7 and a luminosity of 450 suns. This is an eclipsing binary system with the orbital plane being oriented close to the line of sight from the Earth. As a result, an eclipse of one star by the other occurs during each orbit, causing the magnitude to decrease to +3.99. The pair have an orbital period of 972 days (2.66 years) and an eccentricity of 0.4. The primary component has been categorized as a K-type bright giant or supergiant star. Its companion is a B-type main sequence star of stellar classification B5 V or B7 V.
AB Aurigae: How To Make Planets
This enhanced Hubble Space Telescope image shows in remarkable detail the inner portion of the disk of dust and gas surrounding the star AB Aurigae. Knots of material, visible here for the first time, may well represent an early stage of a process which could result in the formation of planets over the next few million years. AB Aurigae is a young star (2-4 million years old), about 469 light-years distant. Its swirling circumstellar disk is large, about 30 times the size of our solar system. Astronomers believe planet-making is just beginning in AB Aurigae's disk because known disks surrounding younger stars (less than 1 million years old) do not show such clumpy structure, while disks of slightly older stars (aged 8-10 million years) have gaps and features suggesting that planets have already been formed. Why the window pane appearance? Wide black stripes in the picture are caused by occulting bars used to block out the overwhelming starlight. The diagonal streaks are due to diffraction spikes.
[http://apod.nasa.gov/apod/ap030208.html]
WISE Catches a Runaway Star in Flames
NASA’s Wide-field Infrared Survey Explorer, or WISE, captured this view of a runaway star racing away from its original home. Seen here surrounded by a glowing cloud of gas and dust, the star AE Aurigae appears to be on fire. Appropriately, the cloud is called the Flaming Star Nebula.
A runaway star is one that is hurled into high-speed motion through a supernovae explosion or collision with nearby stars. Like an angry teenager who storms out of the house after a family fight, runaway stars are ejected from their birthplace and race off to other parts of the Galaxy.
The runaway star AE Aurigae was likely born in Trapezium Cluster, which is located in the constellation Orion. It formed a binary star system with the star Mu Columbae. Approximately 2.5 million years ago, these two stars collided with another binary star system in the Trapezium Cluster. This collision sent both AE Aurigae and Mu Columbae hurtling through space in opposite directions at a speed of 100 kilometers per second. Today, AE Aurigae can be seen in the constellation Auriga, while its former binary star Mu Columbae is located in the constellation Columba.
The wind from AE Aurigae blows away electrons from the gas surrounding it. This ionized gas begins to emit light, creating what is known as an emission nebula. The star also heats up nearby dust, causing it to glow in infrared wavelengths. As seen in visible light, this dust reflects the light of nearby stars, so it is called a reflection nebula.
The colors seen in this image represent specific wavelengths of infrared light. Hot stars scattered throughout the image show up as blue and cyan. Blue represents light emitted at wavelengths of 3.4 microns, while cyan represents 4.6 microns. The gas of the emission nebula appears green, representing 12-micron wavelengths. The dust of the reflection nebula appears primarily red, representing 22-micron light.
One interesting aspect of this image is that the edges of the reflection nebula appear lavender. This is because at its edges the nebula is both emitting light at longer, 22-micron wavelengths and scattering shorter, 3.4-micron wavelength light. Since WISE represents 22-micron light as red and 3.4-micron light as blue, the combination of the two appears in this image as lavender.
Distance: 1500 light years.
[http://wise.ssl.berkeley.edu/gallery_ic405.html]
There are five stars with confirmed planetary systems in Auriga. HD 40979 has one planet, HD 40979 b. It was discovered in 2002 through radial velocity measurements on the parent star. HD 40979 is 33.3 parsecs from Earth, a spectral class F8V star of magnitude 6.74- just past the limit of visibility to the naked eye. It is of similar size to the Sun, at 1.1 solar masses and 1.21 solar radii. The planet, with a mass of 3.83 Jupiter masses, orbits with a semi-major axis of 0.83 AU and a period of 263.1 days. HD 45350 has one planet as well. HD 45350 b was discovered through radial velocity measurements in 2004. It has a mass of 1.79 Jupiter masses and orbits every 890.76 days at a distance of 1.92 AU. Its parent star is faint, at an apparent magnitude of 7.88, 49 parsecs away. It has a mass of 1.02 solar masses and a radius of 1.27 solar radii. HD 43691 b is a significantly larger planet, with a mass of 2.49 Jupiter masses; it is also far closer to its parent star, HD 43691. Discovered in 2007 from radial velocity measurements, it orbits at a distance of 0.24 AU with a period of 36.96 days. HD 43691 has a radius identical to the Sun’s, though it is more dense- its mass is 1.38 solar masses. It is a G0IV type star of magnitude 8.03, 93.2 parsecs from Earth.
Auriga has many open clusters and other objects because the Milky Way runs through it. The three brightest open clusters are M36, M37 and M38, all of which are visible in binoculars or a small telescope in suburban skies. A larger telescope resolves individual stars. Three other open clusters are NGC 2281, lying close to ψ7 Aurigae, NGC 1664, which is close to ε Aurigae, and IC 410 (surrounding NGC 1893), a cluster with nebulosity next to IC 405, the Flaming Star Nebula, found about mid-way between M38 and ι Aurigae;
The Tadpoles of IC 410
This telescopic close-up shows off the otherwise faint emission nebula IC 410 in striking false-colors. It also features two remarkable inhabitants of the cosmic pond of gas and dust below and right of center, the tadpoles of IC 410. The picture is a composite of images taken through narrow band filters. The narrow band image data traces atoms in the nebula, with emission from sulfur atoms in red, hydrogen atoms in green, and oxygen in blue. Partly obscured by foreground dust, the nebula itself surrounds NGC 1893, a young galactic cluster of stars that energizes the glowing gas. Composed of denser cooler gas and dust the tadpoles are around 10 light-years long, potentially sites of ongoing star formation. Sculpted by wind and radiation from the cluster stars, their tails trail away from the cluster’s central region. IC 410 lies some 12,000 light-years away, toward the constellation Auriga.
[http://apod.nasa.gov/apod/ap140109.html]
Another nebula in Auriga, slightly more than one degree to the west of M36, is NGC 1931, considered to be a difficult target for an amateur telescope:
The Spider and the Fly
Star clusters and nebulae abound in the ancient northern constellation Auriga- a region that includes the interesting pair NGC 1931 (lower left) and IC 417. In this gorgeous color image, an imaginative eye toward the expansive IC 417 and diminutive NGC 1931 suggests a cosmic spider and fly. About 10,000 light-years distant, both are young open star clusters formed in interstellar clouds and still embedded in glowing hydrogen gas. The more compact NGC 1931 is about 10 light-years across with contrasting blue hues characteristic of dust reflected starlight.
[http://apod.nasa.gov/apod/ap061027.html]
Auriga is home to the meteor shower of the Aurigids, named for the entire constellation and formerly called the ‘Alpha Aurigids,’ renowned for their intermittent outbursts, such as those in 1935, 1986, 1994, and 2007. The last outburst was observed by astronomers worldwide. Many bright meteors were observed throughout the shower, which peaked on September 1 as predicted. Much like in the 1994 outburst, the 2007 Aurigids were very bright and often colored blue and green. The maximum zenithal hourly rate was 100 meteors per hour, observed by a team of astronomers flying on NASA planes:
Aurigids from 47,000 Feet
On September 1 (2007), Aurigid meteors filled the sky, in keeping with an innovative prediction of an outburst from this historically tentative meteor shower. The prediction was made by Peter Jenniskens of the SETI Institute, in work with Esko Lyytinen of Finland and Jeremie Vaubaillon of Caltech. Astronomers flying at 47,000 feet on a dedicated mission to observe the outburst collected image data for this composite photo of the Aurigids’ bright and colorful streaks. The source of the shower is understood to be Comet Kiess, a comet that would have swung through the inner solar system around 2,000 years ago, and again in 1911. Pushed outward by solar radiation pressure, dust from the tail of the comet has been drifting toward the Earth’s orbit, creating the 2007 outburst as well as outbursts of the Aurigids recorded in 1935, 1986, and 1994. Of course, the shower’s radiant point is in the eponymous constellation Auriga, the Charioteer.
[http://apod.nasa.gov/apod/ap070905.html]
[https://en.wikipedia.org/wiki/Auriga_%28constellation%29]
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