Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||05h 16m 41.3591s[note 1]|
|Declination||+45° 59′ 52.768″[note 1]|
|Apparent magnitude (V)||0.08 (0.03 - 0.16)|
|U−B color index||+0.44|
|B−V color index||+0.80|
|V−R color index||−0.3|
|R−I color index||+0.44|
|Variable type||RS CVn|
|Radial velocity (Rv)||+29.9387 ± 0.0032[note 2] km/s|
|Proper motion (μ)||RA: 75.52[note 1] mas/yr
Dec.: −427.11[note 1] mas/yr
|Parallax (π)||76.20 ± 0.46 mas|
|Distance||13.159 ± 0.015 pc|
|Absolute magnitude (MV)||0.296|
|Absolute magnitude (MV)||0.167|
|Period (P)||104.02128 ± 0.00016 d|
|Semi-major axis (a)||0.056442 ± 0.000023"
(0.74272 ± 0.00069 AU)
|Eccentricity (e)||0.00089 ± 0.00011|
|Inclination (i)||137.156 ± 0.046°|
|Longitude of the node (Ω)||40.522 ± 0.039°|
|Periastron epoch (T)||2448147.6 ± 2.6 JD|
|Argument of periastron (ω)
|342.6 ± 9.0 JD°|
|25.9611 ± 0.0044 km/s|
|26.860 ± 0.0017 km/s|
|Mass||2.5687 ± 0.0074 M☉|
|Radius||11.98 ± 0.57 R☉|
|Luminosity (bolometric)||78.7 ± 4.2 L☉|
|Surface gravity (log g)||2.691 ± 0.041 cgs|
|Temperature||4,970 ± 50 K|
|Metallicity||−0.04 ± 0.06|
|Rotation||104 ± 3|
|Rotational velocity (v sin i)||4.1 ± 0.4 km/s|
|Mass||2.4828 ± 0.0067 M☉|
|Radius||8.83 ± 0.33 R☉|
|Luminosity (bolometric)||72.7 ± 3.6 L☉|
|Surface gravity (log g)||2.941 ± 0.032 cgs|
|Temperature||5,730 ± 60 K|
|Rotation||8.5 ± 0.2|
|Rotational velocity (v sin i)||35.0 ± 0.5 km/s|
|Age||590 - 650 Myr|
Capella, also designated Alpha Aurigae (α Aurigae, abbreviated Alpha Aur, α Aur), is the brightest star in the constellation of Auriga; the sixth-brightest in the night sky and the third-brightest in the northern celestial hemisphere, after Arcturus and Vega.
Although it 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 the Sun.
α Aurigae (Latinised to Alpha Aurigae) is the star's Bayer designation. The traditional name Capella (Latin for small female goat) is a diminutive of "Capra" (Latin for female goat). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Capella for this star. It is now so entered in the IAU Catalog of Star Names.
Professor William Wallace Campbell of the Lick Observatory announced that Capella was binary in 1899, based on spectroscopic observations—he noted on photographic plates taken from August 1896 to February 1897 that a second spectrum appeared superimposed over the first, and that there was a doppler shift to violet in September and October and to red in November and February—showing that the components were moving toward and away from the Earth (and hence orbiting each other). Almost simultaneously, British astronomer Hugh Newall had observed its composite spectrum with a four prism spectroscope attached to a 25-inch telescope at Cambridge in July 1899, concluding that it was a binary star system.
Many observers tried to discern the component stars without success. Known as "The Interferometrist's Friend", it was first resolved interferometrically in 1919 by John Anderson and Francis Pease at Mount Wilson Observatory, who published an orbit in 1920 based on their observations. This was the first interferometric measurement of any object outside the Solar System. A high-precision orbit was published in 1994 based on observations by the Mark III Stellar Interferometer, again at Mount Wilson Observatory. Capella also became the first astronomical object to be imaged by a separate element optical interferometer when it was imaged by the Cambridge Optical Aperture Synthesis Telescope in September 1995.
In 1914, Finnish astronomer Ragnar Furuhjelm observed that the spectroscopic binary mentioned above had a faint companion star, which, as its proper motion was similar to that of the spectroscopic binary, was probably physically bound to it. In February 1936, Carl L. Stearns observed that this companion appeared to be double itself; this was confirmed in September that year by Gerard Kuiper.
Capella appears to be a rich yellowish-white color. However, during daylight observation with a telescope, the yellow color is more apparent due to the contrast against the blue sky. It is the brightest star in the constellation Auriga, the sixth-brightest star in the night sky, the third-brightest star in the northern celestial hemisphere (after Arcturus and Vega), and the fourth-brightest star visible to the naked eye from the latitude 40° N. Capella was the brightest star in the night sky from 210,000 years ago to 160,000 years ago, at about −1.8 in magnitude. At −1.1, Aldebaran was brightest before this period, and it and Capella were situated rather close to each other and served as boreal pole stars at the time.
In Bayer's 1603 work Uranometria, Capella marks the charioteer's back. A few degrees to the southwest lie the pair of stars known as "The Kids", or Haedi (Zeta and Eta Aurigae).[note 3] Capella is closer to the north celestial pole than any other first magnitude star[note 4] Its northern declination is such that it is actually invisible south of latitude 44°S—this includes southernmost New Zealand, Argentina and Chile as well as the Falkland Islands. Conversely it is circumpolar north of 44°north: for the whole of the United Kingdom and Scandinavia, most of France, Canada and the northernmost United States, the star never sets. Capella and Vega are on opposite sides of the pole, at about the same distance from it, such that an imaginary line between the two stars will nearly pass through Polaris.
Two Aerobee-Hi rocket flights on September 20, 1962, and March 15, 1963, apparently detected and confirmed an X-ray source in Auriga at RA 05h 09m Dec +45°. It was identified as Capella which is in the error box. Capella was much more readily detected on the second rocket flight. Stellar X-ray astronomy started on April 5, 1974, with the detection of X-rays from Capella. A rocket flight on that date briefly calibrated its attitude control system when a star sensor pointed the payload axis at Capella. During this period, X-rays in the range 0.2–1.6 keV were detected by an X-ray reflector system co-aligned with the star sensor. The X-ray luminosity (Lx) of ~1024 W (1031 erg s−1) is four orders of magnitude above the Sun's X-ray luminosity.
Capella is a source of X-rays, thought to be primarily from the corona of the more massive star. Capella is ROSAT X-ray source 1RXS J051642.2+460001. The high temperature of Capella's corona as obtained from the first coronal X-ray spectrum of Capella using HEAO 1 required magnetic confinement unless it was a free-flowing coronal wind.
The Capella system consists of a bright binary of giant stars, orbiting at some distance from a fainter binary of red dwarfs. The two main stars are Capella Aa and Capella Ab, whereas their faint companions are Capella H and Capella L—the stars labelled Capella C through to G are actually unrelated stars in the same visual field. Based upon an annual parallax shift of 76.20 milliarcseconds (with a margin of error of 0.46 milliarcseconds) as measured by the Hipparcos satellite, this system is estimated to be 42.8 light-years (13.12 parsecs) from Earth, with a margin of error of 0.3 light-years (0.09 parsecs).
In a 1960 paper, American astronomer Olin J. Eggen discerned that Capella was a member of the Hyades moving group, a group of stars moving in the same direction as the Hyades cluster, by analysing its proper motion and parallax. Members of the group are of a similar age, and those that are around 2.5 times as massive as the Sun have moved off the main sequence and are expanding and cooling into red giants. He adopted the spectral values of G8III and G0III, but was concerned the hotter star's properties were not consistent with its companion if of the same age, and that it might have already been a red giant and be heating up once more.
Capella's bright binary consists of two type-G giant stars that have been calculated by Guillermo Torres and colleagues in 2009 to orbit each other every 104 days; the researchers reviewed all spectroscopic and interferometric measurements to date to come up with the properties of the component stars. They calculated that the first, primary, star (Capella Aa) had a surface temperature of around 4920 ± 70 K, a radius of around 11.87 ± 0.56 solar radii, a mass of around 2.466 ± 0.018 solar masses, and a luminosity, measured over all wavelengths, of 79.5 ± 4.8 times that of the Sun. The other, secondary, star (Capella Ab) had a surface temperature of approximately 5680 ± 70 K, a radius of 8.75 ± 0.32 solar radii, a mass of around 2.443 ± 0.013 solar masses, and a luminosity, again measured over all wavelengths, around 72.1 ± 3.6 times that of the Sun. In 2011, Weber and Strassmeier calculated masses for the pair of 2.573±0.009 and 2.488±0.008 solar masses for the primary and secondary respectively after reviewing 438 echelle spectrographs taken over three and a half years. Although Capella Aa is the brighter star when considering radiation at all wavelengths, it is the fainter when observed in visible light, with an apparent magnitude of 0.91, compared to the secondary's apparent magnitude of 0.76.
The system has been classified as a RS Canum Venaticorum variable, a class of binary stars with active chromospheres that cause large starspots. Unusually for these systems, the hotter star, Capella Ab, has the more active atmosphere. It is likely to be located in the Hertzsprung gap—a stage where it is changing its angular momentum and deepening its convection zone.
The pair is a non-eclipsing binary—that is, as seen from Earth, neither star passes in front of the other. The two components orbit each other at a distance of around 100 million km and an orbital period of approximately 104 days. The stars were probably of spectral class A during their main-sequence lifetime, similar to Vega; they are now expanding, cooling, and brightening to become red giants, a process that will take a few million years. It is thought that the more massive star of the pair has begun fusing helium to carbon and oxygen at its center, a process that has not yet begun for the less massive star.
The double companion star is a binary system of red dwarfs, thought to be separated from the pair of G-type giants by a distance of around 10,000 AU. Although this pair has only been observed to cover approximately 30° of its orbit, a rough, preliminary orbit has been computed, giving an orbital period of approximately 400 years.
Etymology and cultural significance
Capella traditionally marks the left shoulder of the constellation's eponymous charioteer, or, according to the 2nd century astronomer Ptolemy's Almagest, the goat that the charioteer is carrying. In Greek mythology, the star represented the goat Amalthea that suckled Zeus. It was this goat whose horn, after accidentally being broken off by Zeus, was transformed into the Cornucopia, or "horn of plenty", which would be filled with whatever its owner desired. Capella forms an asterism with the stars Epsilon, Zeta, and Eta Aurigae, the latter two of which are known as the Haedi (the Kids). 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. The asterism containing the three goats had been a separate constellation; however, Ptolemy merged the Charioteer and the Goats in the 2nd century Almagest. Before that, 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".
This symbolism dates back to Mesopotamia as a constellation called GAM, representing a scimitar or crook. It may have represented Capella alone 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. It is sometimes called the Shepherd's Star in English literature. Capella is thought to be mentioned in an Akkadian inscription dating to the 20th century BC.
In medieval accounts, it also has the uncommon name Alhajoth (also spelled Alhaior, Althaiot, Alhaiset, Alhatod, Alhojet, Alanac, Alanat, Alioc), which (especially the last) may be a corruption of its Arabic name, العيوق, al-cayyūq. cAyyūq has no clear significance in Arabic, but may be an Arabized form of the Greek αίξ aiks "goat"; cf. the modern Greek Αίγα Aiga, the feminine of goat. To the Bedouin of the Negev and Sinai, Capella al-‘Ayyūq ath-Thurayyā "Capella of the Pleiades", from its role as pointing out the position of that asterism. Another name in Arabic was Al-Rākib "the driver", a translation of the Greek.
Conversely in Slavic Macedonian folklore, Capella was Jastreb "the hawk", flying high above and ready to pounce on Mother Hen (the Pleiades) and the Rooster (Nath).
Astrologically, Capella portends civic and military honors and wealth. In the Middle Ages, it was considered a Behenian fixed star, with the stone sapphire and the plants horehound, mint, mugwort, and mandrake as attributes. Cornelius Agrippa listed its kabbalistic sign with the name Hircus (Latin for goat).
In Hindu mythology, Capella was seen as the heart of Brahma, Brahma Hṛdaya. In traditional Chinese astronomy, Capella was part of the asterism 五車 (Simplified Chinese: 五车; Wŭ chē; English: Five Chariots), which consisted of Capella together with β, ι, and θ Aurigae, as well as β Tauri. Since it was the second star in this asterism, it has the name 五車二 (Simplified Chinese: 五车二; Wŭ chē èr; English: Second of the Five Chariots).
In Inuit astronomy, Capella, along with Menkalinan (Beta Aurigae), Pollux (Beta Geminorum) and Castor (Alpha Geminorum), formed a constellation Quturjuuk, "collar-bones", the two pairs of stars denoting a bone each. Used for navigation and time-keeping at night, the constellation was recognised from Alaska to western Greenland.
The Hawaiians saw Capella as part of an asterism Ke ka o Makali'i ("The canoe bailer of Makali'i") that helped them navigate at sea. Called Hoku-lei "star wreath", it formed this asterism with Procyon, Sirius, Castor and Pollux. In Tahitian folklore, Capella was Tahi-ari'i, the wife of Fa'a-nui (Auriga) and mother of prince Ta'urua (Venus) who sails his canoe across the sky.
In Australian Aboriginal mythology for the Boorong people of Victoria, Capella was Purra, the kangaroo, pursued and killed by the nearby Gemini twins, Yurree (Castor) and Wanjel (Pollux). The Wardaman people of northern Australia knew the star as Yagalal, a ceremonial fish scale, related to Guwamba the barramundi (Aldebaran).
- USS Capella (AK-13) and USNS Capella (T-AKR-293), both of United States Navy ships.
- Mazda Capella, a model of automobile manufactured by Mazda
In addition to the stars mentioned above, Capella has six additional visual companions—that is, stars that appear to be close to Capella in the sky. However, they are not thought to be physically close to Capella. They are shown in the table below.
|Multiple/double star designation: WDS 05167+4600|
|B||A||05h 16m 42.7s||+46° 00′ 55″||1898||46.6″||23°||17.1||Simbad|
|C||A||05h 16m 35.9s||+46° 01′ 12″||1878||78.2″||318°||15.1||Simbad|
|D||A||05h 16m 40.1s||+45° 58′ 07″||1878||126.2″||183°||13.6||Simbad|
|E||A||05h 16.5m||+46° 02′||1908||154.1″||319°||12.1||Simbad|
|F||A||05h 16m 48.748s||+45° 58′ 30.84″||1999||112.0″||137°||10.21||Simbad|
|G||A||05h 16m 31.852s||+46° 08′ 27.42″||2003||522.4″||349°||8.10||Simbad|
- Astrometric data, mirrored by SIMBAD from the Hipparcos catalogue, pertains to the center of mass of the Capella Aa/Ab binary system. See Volume 1, The Hipparcos and Tycho Catalogues, European Space Agency, 1997, §2.3.4, and the entry in the Hipparcos catalogue (CDS ID I/239.)
- Radial velocity figure is for the center of mass of the Capella Aa/Ab binary system.
- The cooler and more massive star, the spectroscopic primary, is the visually fainter star. See Hummel et al. 1994, §1.
- Polaris is only second magnitude.
- NAME CAPELLA – Variable of RS CVn type, database entry, SIMBAD. Accessed on line December 23, 2008.
- Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven, Conn.: Yale University Observatory, 5th rev.ed. Bibcode:1991bsc..book.....H.
- Petit, M. (1990). "Catalogue of Variable or Suspected Stars Nearby the Sun". Astronomy and Astrophysics Supplement. 85: 971. Bibcode:1990A&AS...85..971P.
- Strassmeier, K. G.; Fekel, F. C. (1990). "The spectral classification of chromospherically active binary stars with composite spectra". Astronomy and Astrophysics. 230: 389. Bibcode:1990A&A...230..389S.
- Torres, Guillermo; Claret, Antonio; Pavlovski, Krešimir; Dotter, Aaron (2015). "Capella (α Aurigae) Revisited: New Binary Orbit, Physical Properties, and Evolutionary State". The Astrophysical Journal. 807: 26. arXiv: . Bibcode:2015ApJ...807...26T. doi:10.1088/0004-637X/807/1/26.
- van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–64. arXiv: . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- Sirius Matters, Noah Brosch, Springer: 2008, ISBN 1-4020-8318-1, p. 46.
- Entry 05167+4600, The Washington Double Star Catalog, United States Naval Observatory. Accessed on line December 24, 2008.
- Star-names and Their Meanings, Richard Hinckley Allen, New York: G. E. Stechert, 1899; see p. 86.
- "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
- "IAU Catalog of Star Names". Retrieved 28 July 2016.
- Campbell, William Wallace (October 1899). "The Spectroscopic Binary Capella". Astrophysical Journal. 10: 177. Bibcode:1899ApJ....10..177C. doi:10.1086/140625.
- Newall, Hugh Frank (December 1899). "Variable Velocities of Stars in the Line of Sight". The Observatory. 22: 436–37. Bibcode:1899Obs....22..436N.
- Newall, Hugh Frank (March 1900). "The Binary System of Capella". Monthly Notices of the Royal Astronomical Society. 60 (6): 418–20. Bibcode:1900MNRAS..60..418N. doi:10.1093/mnras/60.6.418.
- Torres, Guillermo; Claret, Antonio; Young, Patrick A. (2009). "Binary Orbit, Physical Properties, and Evolutionary State of Capella (α Aurigae).". The Astrophysical Journal. 700 (2): 1349–81. arXiv: . Bibcode:2009ApJ...700.1349T. doi:10.1088/0004-637X/700/2/1349.
- Mason, B. (August 22–25, 2006). "Classical Observations of Visual Binary and Multiple Stars". In William I. Hartkopf; Edward F. Guinan; Petr Harmanec. Binary Stars as Critical Tools and Tests in Contemporary Astrophysics, Proceedings of the 240th Symposium of the International Astronomical Union, Held in Prague, Czech Republic. Cambridge University Press. pp. 88–96 . doi:10.1017/S1743921307003857. ISBN 0-521-86348-1.
- Anderson, J.A. (1920). "Application of Michelson's Interferometer Method to the Measurement of Close Double Stars". Astrophysical Journal. 51: 263–75. Bibcode:1920ApJ....51..263A. doi:10.1086/142551.
- Modern Optical Interferometry, Astronomical Optical Interferometry: A Literature Review, Bob Tubbs, St. John's College, Cambridge, April 1997. Accessed on line December 30, 2008.
- Very high precision orbit of Capella by long baseline interferometry, C. A. Hummel et al., The Astronomical Journal 107, #5 (May 1994), pp. 1859–1867, doi:10.1086/116995, Bibcode: 1994AJ....107.1859H. See §1 for spectral types, Table 1 for orbit, Table 5 for stellar parameters, and §6.3 for the age of the system.
- Baldwin, J.E.; Beckett, M.G.; Boysen, R.C.; Burns, D.; Buscher, D.F.; Cox, G.C.; et al. (1996). "The first images from an optical aperture synthesis array: mapping of Capella with COAST at two epochs". Astronomy and Astrophysics. 306: L13–L16. Bibcode:1996A&A...306L..13B..
- Furuhjelm, Ragnar (April 1914). "Ein schwacher Begleiter zu Capella". Astronomische Nachrichten (in German). 197 (11): 181–182. Bibcode:1914AN....197..181F. doi:10.1002/asna.19141971103. 4715.
- Stearns, Carl L. (July 1936). "Note on duplicity of Capella H". Astronomical Journal. 45 (1048): 120. Bibcode:1936AJ.....45..120S. doi:10.1086/105349..
- Kuiper, Gerard P. (October 1936). "Confirmation of the Duplicity of Capella H". Astrophysical Journal. 84: 359. Bibcode:1936ApJ....84Q.359K. doi:10.1086/143788.
- Schaaf 2008, p. 146.
- Schaaf 2008, p. 155.
- Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, Virginia: The McDonald & Woodward Publishing Company. p. 503. ISBN 978-0-939923-78-6.
- Burnham 1978, p. 261.
- Arnold, H.P. (1999). The Photographic Atlas of the Stars. Bristol, UK: IOP Publishing Ltd. p. 68. ISBN 0750306548.
- Fisher, Philip C.; Meyerott, Arthur J. (1964). "Stellar X-Ray Emission". Astrophysical Journal. 139 (1): 123–42. Bibcode:1964ApJ...139..123F. doi:10.1086/147742.
- Catura, R.C.; Acton, L.W.; Johnson, H.M. (1975). "Evidence for X-ray emission from Capella". Astrophysical Journal. 196 (pt.2): L47–49. Bibcode:1975ApJ...196L..47C. doi:10.1086/181741.
- Ishibashi, Kazunori; Dewey, Daniel; Huenemoerder, David P.; Testa, Paola (2006). "Chandra/HETGS Observations of the Capella System: The Primary as a Dominating X-Ray Source". The Astrophysical Journal. 644 (2): L117–L120. arXiv: . Bibcode:2006ApJ...644L.117I. doi:10.1086/505702.
- Güdel, Manuel (2004). "X-ray astronomy of stellar coronae". The Astronomy and Astrophysics Review. 12 (2–3): 71–237. arXiv: . Bibcode:2004A&ARv..12...71G. doi:10.1007/s00159-004-0023-2.
- Capella HL, T. R. Ayres, pp. 202–204, in Cool Stars, Stellar Systems, and the Sun: Proceedings of the Third Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Held in Cambridge, Massachusetts, October 5–7, 1983, edited by Sallie L. Baliunas and Lee Hartmann, Berlin/Heidelberg, Springer-Verlag, 1984, Lecture Notes in Physics, vol. 193, ISBN 978-3-540-12907-3; doi:10.1007/3-540-12907-3_204, Bibcode: 1984LNP...193..202A
- Schaaf, p. 154.
- Eggen, Olin J (1960). "Stellar Groups, VII. The Structure of the Hyades Group". Monthly Notices of the Royal Astronomical Society. 120 (6): 540–62. Bibcode:1960MNRAS.120..540E. doi:10.1093/mnras/120.6.540.
- Weber, M.; Strassmeier, K.G. (2011). "The Spectroscopic Orbit of Capella Revisited". Astronomy & Astrophysics. 531: id.A89 (5 pp.). arXiv: . Bibcode:2011A&A...531A..89W. doi:10.1051/0004-6361/201116885.
- The Brightest Stars: Discovering the Universe through the Sky's Most Brilliant Stars, Fred Schaaf, Hoboken, New Jersey: John Wiley & Sons, 2008, ISBN 978-0-471-70410-2; see pp. 153–155.
- G 96-29 – High proper-motion Star, database entry, SIMBAD. Accessed on line December 23, 2008.
- NAME CAPELLA L – Star in double system, database entry, SIMBAD. Accessed on line December 23, 2008.
- Chromospheric activity, kinematics, and metallicities of nearby M dwarfs, J. R. Stauffer and L. W. Hartmann, Astrophysical Journal Supplement Series 61 (July 1986), pp. 531–568, Bibcode: 1986ApJS...61..531S, doi:10.1086/191123; see Table 1.
- Infrared Spectra of Low-Mass Stars: Toward a Temperature Scale for Red Dwarfs, by S. K. Leggett, F. Allard, Graham Berriman, Conard C. Dahn, and Peter H. Hauschildt, Astrophysical Journal Supplement 104 (May 1996), pp. 117–143, Bibcode: 1996ApJS..104..117L, doi:10.1086/192295; see Tables 3, 6 and 7.
- Johnson, H. M. (1983). "Origins and ages of X-ray-luminous dwarf M stars". Astrophysical Journal. 273: 702. Bibcode:1983ApJ...273..702J. doi:10.1086/161405.
- Parallax and motions of the Capella system, W. D. Heintz, Astrophysical Journal 195 (January 1975), pp. 411–412, doi:10.1086/153340, Bibcode: 1975ApJ...195..411H
- Multiplicity among M dwarfs, Debra A. Fischer and Geoffrey W. Marcy, The Astrophysical Journal 396, #1 (September 1, 1992), pp. 178–194, Bibcode: 1992ApJ...396..178F, doi:10.1086/171708; see Table 1.
- Schaaf 2008, p. 152.
- Moore & Tirion 1997, p. 130–131.
- Ridpath & Tirion 2001, pp. 86–88.
- Ridpath, Ian. "Auriga". Star Tales. self-published. Retrieved 4 March 2014.
- Winterburn 2009, p. 131.
- Allen 1899, pp. 83–91.
- Rogers, John H. (1998). "Origins of the Ancient Constellations: I. The Mesopotamian traditions". Journal of the British Astronomical Association. 108 (1): 9–28. Bibcode:1998JBAA..108....9R.
- Allen 1899, p. 88.
- Allen 1899, p. 85.
- Edward William Lane's Arabic-English Lexicon: cwq
- Allen 1899, p. 87.
- Bedouin Star-Lore in Sinai and the Negev, Clinton Bailey, Bulletin of the School of Oriental and African Studies, University of London 37, #3 (1974), pp. 580–596; see p. 595.
- Cenev, Gjore (2008). "Macedonian Folk Constellations". Publications of the Astronomical Observatory of Belgrade. 85: 97–109. Bibcode:2008POBeo..85...97C.
- The Philosophy of Natural Magic, Heinrich Cornelius Agrippa, Forgotten Books, 2008. ISBN 1-60680-260-7; see p. 85.
- (Latin) De occulta philosophia, Henricus Cornelius Agrippa ab Nettesheym; edited and with commentary by Karl Anton Nowotny, Graz: Akademische Druck-u. Verlagsanstalt, 1967; see pp. 49, 209, 447.
- (Chinese) AEEA 天文教育資訊網, Activities of Exhibition and Education in Astronomy, National Museum of Natural Science, Taiwan. Accessed on line December 31, 2008.
- Exploring Ancient Skies: An Encyclopedic Survey of Archaeoastronomy, David H. Kelley, E. F. Milone, and Anthony F. Aveni, Birkhäuser, 2005, ISBN 0-387-95310-8; see p. 322.
- (Chinese) 香港太空 館 – 研究資源 – 亮星中英對照表 Archived September 29, 2009, at the Wayback Machine., Hong Kong Space Museum. Accessed on line December 31, 2008.
- MacDonald, John (1998). The Arctic Sky: Inuit Astronomy, Star Lore, and Legend. Toronto, Ontario: Royal Ontario Museum/Nunavut Research Institute. pp. 65–67. ISBN 978-0-88854-427-8.
- Brosch, Noah (2008). Sirius Matters. Springer. p. 46. ISBN 1-4020-8318-1.
- Henry, Teuira (1907). "Tahitian Astronomy: Birth of Heavenly Bodies". The Journal of the Polynesian Society. 16 (2): 101–04. JSTOR 20700813.
- On the astronomy and mythology of the Aborigines of Victoria, W. E. Stanbridge, Proc. of the Philosophical Institute of Victoria, Transactions 2 (1857), pp. 137–140; see p. 140.
- Harney, Bill Yidumduma; Cairns, Hugh C. (2004) . Dark Sparklers (Revised ed.). Merimbula, New South Wales: Hugh C. Cairns. pp. 204–05. ISBN 0-9750908-0-1.
- Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System, Robert Burnham, Courier Dover Publications, 1978, ISBN 0-486-23567-X; see vol. 1, p. 264.
- BD+45 1077B – Star in double system, database entry, SIMBAD. Accessed on line December 24, 2008.
- BD+45 1077C – Star in double system, database entry, SIMBAD. Accessed on line December 24, 2008.
- BD+45 1077D – Star in double system, database entry, SIMBAD. Accessed on line December 24, 2008.
- BD+45 1077E – Star in double system, database entry, SIMBAD. Accessed on line December 24, 2008.
- BD+45 1077F – Star in double system, database entry, SIMBAD. Accessed on line December 24, 2008.
- BD+45 1077G – Star in double system, database entry, SIMBAD. Accessed on line December 24, 2008.
- Moore, Patrick; Tirion, Wil (1997). Cambridge Guide to Stars and Planets (2nd ed.). Cambridge, United Kingdom: Cambridge University Press. ISBN 978-0-521-58582-8.
- Ridpath, Ian; Tirion, Wil (2001). Stars and Planets Guide. Princeton, New Jersey: Princeton University Press. ISBN 978-0-691-08913-3.
- HR 1708, catalog entry, Bright Star Catalogue.
- GJ 194, catalog entry, Preliminary Version of the Third Catalogue of Nearby Stars, W. Gliese and H. Jahreiss, 1991, CDS ID V/70A.
- Images of the bright binary pair from 13 September 1995[permanent dead link] and 28 September 1995[permanent dead link] (note fainter blobs are just noise)