Arcturus is the brightest star in the northern constellation of Boötes. With an apparent visual magnitude of −0.05, it is the fourth-brightest star in the night sky, and the brightest in the northern celestial hemisphere. The name Arcturus originated from ancient Greece; it was then cataloged as α Boötis by Johann Bayer in 1603, which is Latinized to Alpha Boötis. Arcturus forms one corner of the Spring Triangle asterism.
Epoch J2000 Equinox J2000
|Right ascension||14h 15m 39.7s|
|Declination||+19° 10′ 56″|
|Apparent magnitude (V)||−0.05|
|Spectral type||K1.5 III Fe−0.5|
|Apparent magnitude (J)||−2.25|
|U−B color index||+1.28|
|B−V color index||+1.23|
|R−I color index||+0.65|
|Note (category: variability):||H and K emission vary.|
|Radial velocity (Rv)||−5.19 km/s|
|Proper motion (μ)|| RA: −1093.45 mas/yr |
Dec.: −1999.40 mas/yr
|Parallax (π)||88.83 ± 0.54 mas|
|Distance||36.7 ± 0.2 ly |
(11.26 ± 0.07 pc)
|Absolute magnitude (MV)||−0.30±0.02|
|Surface gravity (log g)||1.66±0.05 cgs|
|Metallicity [Fe/H]||−0.52±0.04 dex|
|Rotational velocity (v sin i)||2.4±1.0 km/s|
Bright Star Catalogue (5th rev. ed.),
VizieR catalog entry
Located relatively close at 36.7 light-years from the Sun, Arcturus is a single red giant of spectral type K1.5III—an aging star around 7.1 billion years old that has used up its core hydrogen and evolved off the main sequence. It is about the same mass as the Sun, but has expanded to 25 times its size and is around 170 times as luminous. Its diameter is 35 million kilometres. Thus far no companion has been detected.
The traditional name Arcturus is Latinised from the ancient Greek Ἀρκτοῦρος (Arktouros) and means "Guardian of the Bear", ultimately from ἄρκτος (arktos), "bear" and οὖρος (ouros), "watcher, guardian".
The designation of Arcturus as α Boötis (Latinised to Alpha Boötis) was made by Johann Bayer in 1603. 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 Arcturus for α Boötis.
With an apparent visual magnitude of −0.05, Arcturus is the brightest star in the northern celestial hemisphere and the fourth-brightest star in the night sky, after Sirius (−1.46 apparent magnitude), Canopus (−0.72) and α Centauri (combined magnitude of −0.27). However, α Centauri AB is a binary star, whose components are both fainter than Arcturus. This makes Arcturus the third-brightest individual star, just ahead of α Centauri A (officially named Rigil Kentaurus), whose apparent magnitude is −0.01. The French mathematician and astronomer Jean-Baptiste Morin observed Arcturus in the daytime with a telescope in 1635, a first for any star other than the Sun and supernovae. Arcturus has been seen at or just before sunset with the naked eye.
Arcturus is visible from both of Earth's hemispheres as it is located 19° north of the celestial equator. The star culminates at midnight on 27 April, and at 9 p.m. on June 10 being visible during the late northern spring or the southern autumn. From the northern hemisphere, an easy way to find Arcturus is to follow the arc of the handle of the Big Dipper (or Plough in the UK). By continuing in this path, one can find Spica, "Arc to Arcturus, then spike (or speed on) to Spica". Together with the bright stars Spica and Denebola (or Regulus, depending on the source), Arcturus is part of the Spring Triangle asterism. With Cor Caroli, these four stars form the Great Diamond asterism.
η Boötis, or Muphrid, is only 3.3 light-years distant from Arcturus, and would have a visual magnitude −2.5, about as bright as Jupiter at its brightest from Earth, whereas an observer on the former system would find Arcturus with a magnitude -5.0, slightly brighter than Venus as seen from Earth, but with an orangish color.
Physical characteristics edit
Based upon an annual parallax shift of 88.83 milliarcseconds as measured by the Hipparcos satellite, Arcturus is 36.7 light-years (11.26 parsecs) from the Sun. The parallax margin of error is 0.54 milliarcseconds, translating to a distance margin of error of ±0.23 light-years (0.069 parsecs). Because of its proximity, Arcturus has a high proper motion, two arcseconds a year, greater than any first magnitude star other than α Centauri.
Arcturus is moving rapidly (122 km/s or 270,000 mph) relative to the Sun, and is now almost at its closest point to the Sun. Closest approach will happen in about 4,000 years, when the star will be a few hundredths of a light-year closer to Earth than it is today. (In antiquity, Arcturus was closer to the centre of the constellation.) Arcturus is thought to be an old-disk star, and appears to be moving with a group of 52 other such stars, known as the Arcturus stream.
With an absolute magnitude of −0.30, Arcturus is, together with Vega and Sirius, one of the most luminous stars in the Sun's neighborhood. It is about 110 times brighter than the Sun in visible light wavelengths, but this underestimates its strength as much of the light it gives off is in the infrared; total (bolometric) power output is about 180 times that of the Sun. With a near-infrared J band magnitude of −2.2, only Betelgeuse (−2.9) and R Doradus (−2.6) are brighter. The lower output in visible light is due to a lower efficacy as the star has a lower surface temperature than the Sun.
As a single star, the mass of Arcturus cannot be measured directly, but models suggest it is slightly greater than that of the Sun. Evolutionary matching to the observed physical parameters gives a mass of 1.08±0.06 M☉, while the oxygen isotope ratio for a first dredge-up star gives a mass of 1.2 M☉. Given the star's evolutionary state, it is expected to have undergone significant mass loss in the past. The star displays magnetic activity that is heating the coronal structures, and it undergoes a solar-type magnetic cycle with a duration that is probably less than 14 years. A weak magnetic field has been detected in the photosphere with a strength of around half a gauss. The magnetic activity appears to lie along four latitudes and is rotationally modulated.
Arcturus is estimated to be around 6 to 8.5 billion years old, but there is some uncertainty about its evolutionary status. Based upon the color characteristics of Arcturus, it is currently ascending the red-giant branch and will continue to do so until it accumulates a large enough degenerate helium core to ignite the helium flash. It has likely exhausted the hydrogen from its core and is now in its active hydrogen shell burning phase. However, Charbonnel et al. (1998) placed it slightly above the horizontal branch, and suggested it has already completed the helium flash stage.
Arcturus has evolved off the main sequence to the red giant branch, reaching an early K-type stellar classification. It is frequently assigned the spectral type of K0III, but in 1989 was used as the spectral standard for type K1.5III Fe−0.5, with the suffix notation indicating a mild underabundance of iron compared to typical stars of its type. As the brightest K-type giant in the sky, it has been the subject of multiple atlases with coverage from the ultraviolet to infrared.
The spectrum shows a dramatic transition from emission lines in the ultraviolet to atomic absorption lines in the visible range and molecular absorption lines in the infrared. This is due to the optical depth of the atmosphere varying with wavelength. The spectrum shows very strong absorption in some molecular lines that are not produced in the photosphere but in a surrounding shell. Examination of carbon monoxide lines show the molecular component of the atmosphere extending outward to 2–3 times the radius of the star, with the chromospheric wind steeply accelerating to 35–40 km/s in this region.
Astronomers term "metals" those elements with higher atomic numbers than helium. The atmosphere of Arcturus has an enrichment of alpha elements relative to iron but only about a third of solar metallicity. Arcturus is possibly a Population II star.
As one of the brightest stars in the sky, Arcturus has been the subject of a number of studies in the emerging field of asteroseismology. Belmonte and colleagues carried out a radial velocity (Doppler shift of spectral lines) study of the star in April and May 1988, which showed variability with a frequency of the order of a few microhertz (μHz), the highest peak corresponding to 4.3 μHz (2.7 days) with an amplitude of 60 ms−1, with a frequency separation of c. 5 μHz. They suggested that the most plausible explanation for the variability of Arcturus is stellar oscillations.
Asteroseismological measurements allow direct calculation of the mass and radius, giving values of 0.8±0.2 M☉ and 27.9±3.4 R☉. This form of modelling is still relatively inaccurate, but a useful check on other models.
Possible planetary system edit
Hipparcos satellite astrometry suggested that Arcturus is a binary star, with the companion about twenty times dimmer than the primary and orbiting close enough to be at the very limits of humans' current ability to make it out. Recent results remain inconclusive, but do support the marginal Hipparcos detection of a binary companion.
In 1993, radial velocity measurements of Aldebaran, Arcturus and Pollux showed that Arcturus exhibited a long-period radial velocity oscillation, which could be interpreted as a substellar companion. This substellar object would be nearly 12 times the mass of Jupiter and be located roughly at the same orbital distance from Arcturus as the Earth is from the Sun, at 1.1 astronomical units. However, all three stars surveyed showed similar oscillations yielding similar companion masses, and the authors concluded that the variation was likely to be intrinsic to the star rather than due to the gravitational effect of a companion. So far no substellar companion has been confirmed.
One astronomical tradition associates Arcturus with the mythology around Arcas, who was about to shoot and kill his own mother Callisto who had been transformed into a bear. Zeus averted their imminent tragic fate by transforming the boy into the constellation Boötes, called Arctophylax "bear guardian" by the Greeks, and his mother into Ursa Major (Greek: Arctos "the bear"). The account is given in Hyginus's Astronomy.
An alternative lore associates the name with the legend around Icarius, who gave the gift of wine to other men, but was murdered by them, because they had had no experience with intoxication and mistook the wine for poison. It is stated this Icarius, became Arcturus, while his dog, Maira, became Canicula (Procyon), although "Arcturus" here may be used in the sense of the constellation rather than the star.
Cultural significance edit
As one of the brightest stars in the sky, Arcturus has been significant to observers since antiquity.
In ancient Mesopotamia, it was linked to the god Enlil, and also known as Shudun, "yoke", or SHU-PA of unknown derivation in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC.
In ancient Greek the star is found in ancient astronomical literature, e.g. Hesiod's Work and Days, circa 700 BC, as well as Hipparchus's and Ptolemy's star catalogs. The folk-etymology connecting the star name with the bears (Greek: ἄρκτος, arktos) was probably invented much later. It fell out of use in favour of Arabic names until it was revived in the Renaissance.
In Arabic, Arcturus is one of two stars called al-simāk "the uplifted ones" (the other is Spica). Arcturus is specified as السماك الرامح as-simāk ar-rāmiħ "the uplifted one of the lancer". The term Al Simak Al Ramih has appeared in Al Achsasi Al Mouakket catalogue (translated into Latin as Al Simak Lanceator). This has been variously romanized in the past, leading to obsolete variants such as Aramec and Azimech. For example, the name Alramih is used in Geoffrey Chaucer's A Treatise on the Astrolabe (1391). Another Arabic name is Haris-el-sema, from حارس السماء ħāris al-samā’ "the keeper of heaven". or حارس الشمال ħāris al-shamāl’ "the keeper of north".
In Indian astronomy, Arcturus is called Swati or Svati (Devanagari स्वाति, Transliteration IAST svāti, svātī́), possibly 'su' + 'ati' ("great goer", in reference to its remoteness) meaning very beneficent. It has been referred to as "the real pearl" in Bhartṛhari's kāvyas.
In Chinese astronomy, Arcturus is called Da Jiao (Chinese: 大角; pinyin: Dàjiǎo; lit. 'great horn'), because it is the brightest star in the Chinese constellation called Jiao Xiu (Chinese: 角宿; pinyin: Jiǎo Xiǔ; lit. 'horn star'). Later it became a part of another constellation Kang Xiu (Chinese: 亢宿; pinyin: Kàng Xiǔ).
The Wotjobaluk Koori people of southeastern Australia knew Arcturus as Marpean-kurrk, mother of Djuit (Antares) and another star in Boötes, Weet-kurrk (Muphrid). Its appearance in the north signified the arrival of the larvae of the wood ant (a food item) in spring. The beginning of summer was marked by the star's setting with the Sun in the west and the disappearance of the larvae. The people of Milingimbi Island in Arnhem Land saw Arcturus and Muphrid as man and woman, and took the appearance of Arcturus at sunrise as a sign to go and harvest rakia or spikerush. The Weilwan of northern New South Wales knew Arcturus as Guembila "red".: 84
Prehistoric Polynesian navigators knew Arcturus as Hōkūleʻa, the "Star of Joy". Arcturus is the zenith star of the Hawaiian Islands. Using Hōkūleʻa and other stars, the Polynesians launched their double-hulled canoes from Tahiti and the Marquesas Islands. Traveling east and north they eventually crossed the equator and reached the latitude at which Arcturus would appear directly overhead in the summer night sky. Knowing they had arrived at the exact latitude of the island chain, they sailed due west on the trade winds to landfall. If Hōkūleʻa could be kept directly overhead, they landed on the southeastern shores of the Big Island of Hawaii. For a return trip to Tahiti the navigators could use Sirius, the zenith star of that island. Since 1976, the Polynesian Voyaging Society's Hōkūleʻa has crossed the Pacific Ocean many times under navigators who have incorporated this wayfinding technique in their non-instrument navigation.
Arcturus had several other names that described its significance to indigenous Polynesians. In the Society Islands, Arcturus, called Ana-tahua-taata-metua-te-tupu-mavae ("a pillar to stand by"), was one of the ten "pillars of the sky", bright stars that represented the ten heavens of the Tahitian afterlife. In Hawaii, the pattern of Boötes was called Hoku-iwa, meaning "stars of the frigatebird". This constellation marked the path for Hawaiʻiloa on his return to Hawaii from the South Pacific Ocean. The Hawaiians called Arcturus Hoku-leʻa. It was equated to the Tuamotuan constellation Te Kiva, meaning "frigatebird", which could either represent the figure of Boötes or just Arcturus. However, Arcturus may instead be the Tuamotuan star called Turu. The Hawaiian name for Arcturus as a single star was likely Hoku-leʻa, which means "star of gladness", or "clear star". In the Marquesas Islands, Arcturus was probably called Tau-tou and was the star that ruled the month approximating January. The Māori and Moriori called it Tautoru, a variant of the Marquesan name and a name shared with Orion's Belt.
Early-20th-century Armenian scientist Nazaret Daghavarian theorized that the star commonly referred to in Armenian folklore as Gutani astgh (Armenian: Գութանի աստղ; lit. star of the plow) was in fact Arcturus, as the constellation of Boötes was called "Ezogh" (Armenian: Եզող; lit. the person who is plowing) by Armenians.
In popular culture edit
In Ancient Rome, the star's celestial activity was supposed to portend tempestuous weather, and a personification of the star acts as narrator of the prologue to Plautus' comedy Rudens (circa 211 BC).
One of the possible etymologies offered for the name "Arthur" assumes that it is derived from "Arcturus" and that the late 5th to early 6th-century figure on whom the myth of King Arthur is based was originally named for the star.
In the Middle Ages, Arcturus was considered a Behenian fixed star and attributed to the stone Jasper and the plantain herb. Cornelius Agrippa listed its kabbalistic sign under the alternate name Alchameth.
Arcturus's light was employed in the mechanism used to open the 1933 Chicago World's Fair. The star was chosen as it was thought that light from Arcturus had started its journey at about the time of the previous Chicago World's Fair in 1893 (at 36.7 light-years away, the light actually started in 1896).
At the height of the American Civil War, President Abraham Lincoln observed Arcturus through a 9.6-inch refractor telescope when he visited the Naval Observatory in Washington, DC, in August, 1863.
- van Leeuwen, Florian (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. Paris, France. 474 (2): 653–64. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
- Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
- Massarotti, Alessandro; Latham, David W.; Stefanik, Robert P.; Fogel, Jeffrey (2008). "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity". The Astronomical Journal. 135 (1): 209–231. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.
- Perryman; et al. (1997). "HIP 69673". The Hipparcos and Tycho Catalogues.
- Carney, Bruce W.; et al. (March 2008). "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars". The Astronomical Journal. Paris, France: EDP Sciences. 135 (3): 892–906. arXiv:0711.4984. Bibcode:2008AJ....135..892C. doi:10.1088/0004-6256/135/3/892. S2CID 2756572.
- Ramírez, I.; Allende Prieto, C. (December 2011). "Fundamental Parameters and Chemical Composition of Arcturus". The Astrophysical Journal. Bristol, England: IOP Publishing. 743 (2): 135. arXiv:1109.4425. Bibcode:2011ApJ...743..135R. doi:10.1088/0004-637X/743/2/135. S2CID 119186472.
- Schröder, K.-P.; Cuntz, M. (April 2007). "A critical test of empirical mass loss formulas applied to individual giants and supergiants". Astronomy and Astrophysics. Bristol, England: IOP Publishing. 465 (2): 593–601. arXiv:astro-ph/0702172. Bibcode:2007A&A...465..593S. doi:10.1051/0004-6361:20066633. S2CID 55901104.
- Liddell, Henry George; Scott, Robert. "Ἀρκτοῦρος". A Greek-English Lexicon. Retrieved 2019-01-16.
- Liddell, Henry George; Scott, Robert. "ἄρκτος". A Greek-English Lexicon. Retrieved 2019-01-16.
- Liddell, Henry George; Scott, Robert. "οὖρος". A Greek-English Lexicon. Retrieved 2019-01-16.
- "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.
- Kaler, James B. (2002). The Hundred Greatest Stars. New York City: Copernicus Books. p. 21. ISBN 978-0-387-95436-3.
- Schaaf, Fred (2008). The Brightest Stars: Discovering the Universe Through the Sky's Most Brilliant Stars. Hoboken, New Jersey: John Wiley and Sons. pp. 126–36. Bibcode:2008bsdu.book.....S. ISBN 978-0-471-70410-2.
- Schaaf, p. 257.
- Rao, Joe (June 15, 2007). "Arc to Arcturus, Speed on to Spica". Space.com. Retrieved 14 August 2018.
- "Follow the arc to Arcturus, and drive a spike to Spica | EarthSky.org". earthsky.org. April 8, 2018. Retrieved 14 August 2018.
- Rogers, John H. (1998). "Origins of the Ancient Constellations: II. The Mediterranean Traditions". Journal of the British Astronomical Association. London, England: British Astronomical Association. 108 (2): 79–89. Bibcode:1998JBAA..108...79R.
- Ramya, P.; Reddy, Bacham E.; Lambert, David L. (2012). "Chemical compositions of stars in two stellar streams from the Galactic thick disc". Monthly Notices of the Royal Astronomical Society. 425 (4): 3188. arXiv:1207.0767. Bibcode:2012MNRAS.425.3188R. doi:10.1111/j.1365-2966.2012.21677.x. S2CID 119253279.
- Abia, C.; Palmerini, S.; Busso, M.; Cristallo, S. (2012). "Carbon and oxygen isotopic ratios in Arcturus and Aldebaran. Constraining the parameters for non-convective mixing on the red giant branch". Astronomy & Astrophysics. 548: A55. arXiv:1210.1160. Bibcode:2012A&A...548A..55A. doi:10.1051/0004-6361/201220148. S2CID 56386673.
- Lagarde, N.; et al. (August 2015). "Models of red giants in the CoRoT asteroseismology fields combining asteroseismic and spectroscopic constraints". Astronomy & Astrophysics. 580: A141. arXiv:1505.01529. Bibcode:2015A&A...580A.141L. doi:10.1051/0004-6361/201525856. S2CID 53652388. A141.
- Sennhauser, C.; Berdyugina, S. V. (May 2011). "First detection of a weak magnetic field on the giant Arcturus: remnants of a solar dynamo?". Astronomy & Astrophysics. 529: 6. Bibcode:2011A&A...529A.100S. doi:10.1051/0004-6361/201015445. A100.
- Pavlenko, Ya. V. (September 2008). "The carbon abundance and 12C/13C isotopic ratio in the atmosphere of Arcturus from 2.3 µm CO bands". Astronomy Reports. 52 (9): 749–759. arXiv:0807.3667. Bibcode:2008ARep...52..749P. doi:10.1134/S1063772908090060. S2CID 119268407.
- Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. (2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". The Astronomical Journal. Bristol, England. 126 (4): 2048. arXiv:astro-ph/0308182. Bibcode:2003AJ....126.2048G. doi:10.1086/378365. S2CID 119417105.
- Griffin, R. E.; Griffin, R. (1968). A photometric atlas of the spectrum of Arcturus, λλ3600-8825Å. Cambridge: Cambridge Philosophical Society. Bibcode:1968pmas.book.....G.
- Hinkle, K.; Wallace, L. (2005). "The Spectrum of Arcturus from the Infrared through the Ultraviolet". Cosmic Abundances as Records of Stellar Evolution and Nucleosynthesis. 336: 321. Bibcode:2005ASPC..336..321H.
- Tsuji, T. (2009). "The K giant star Arcturus: The hybrid nature of its infrared spectrum". Astronomy and Astrophysics. 504 (2): 543. arXiv:0907.0065. Bibcode:2009A&A...504..543T. doi:10.1051/0004-6361/200912323. S2CID 6408779.
- Ohnaka, K.; Morales Marín, C. A. L. (November 2018). "Spatially resolving the thermally inhomogeneous outer atmosphere of the red giant Arcturus in the 2.3 μm CO lines". Astronomy & Astrophysics. 620: 10. arXiv:1809.01181. Bibcode:2018A&A...620A..23O. doi:10.1051/0004-6361/201833745. S2CID 119095123. A23.
- Belmonte, J. A.; Jones, A. R.; Palle, P. L.; Roca Cortes, T. (1990). "Acoustic oscillations in the K2 III star Arcturus". Astrophysics and Space Science. 169 (1–2): 77–84. Bibcode:1990Ap&SS.169...77B. doi:10.1007/BF00640689. ISSN 0004-640X. S2CID 120697563.
- Kallinger, T.; Weiss, W. W.; Barban, C.; Baudin, F.; Cameron, C.; Carrier, F.; De Ridder, J.; Goupil, M.-J.; Gruberbauer, M.; Hatzes, A.; Hekker, S.; Samadi, R.; Deleuil, M. (2010). "Oscillating red giants in the CoRoT exofield: Asteroseismic mass and radius determination". Astronomy and Astrophysics. 509: A77. arXiv:0811.4674. Bibcode:2010A&A...509A..77K. doi:10.1051/0004-6361/200811437. S2CID 15061735.
- Verhoelst, T.; Bordé, P. J.; Perrin, G.; Decin, L.; et al. (2005). "Is Arcturus a well-understood K giant?". Astronomy & Astrophysics. 435 (1): 289–301. arXiv:astro-ph/0501669. Bibcode:2005A&A...435..289V. doi:10.1051/0004-6361:20042356. S2CID 14176311., and see references therein.
- Hatzes, A.; Cochran, W. (August 1993). "Long-period radial velocity variations in three K giants". The Astrophysical Journal. 413 (1): 339–348. Bibcode:1993ApJ...413..339H. doi:10.1086/173002.
- Eratosthenes; Hyginus; Aratus (2015). Eratosthenes and Hyginus: Constellation Myths, with Aratus's Phaenomena. Hard, Robin (transl.). Oxford University Press. pp. 5–7, 35–37. ISBN 9780198716983.
- Ridpath, Ian. "Star Tales Boötes". Retrieved 27 November 2022.
- Eratosthenes et al. (2015), pp. 38–40, p. 182 (note to p. 40)
- 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.
- Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, MA: Sky Pub. p. 19. ISBN 978-1-931559-44-7.
- Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society. 55 (8): 429. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.
- "List of the 25 brightest stars". Jordanian Astronomical Society. Archived from the original on March 16, 2012. Retrieved March 28, 2007.
- Allen, Richard Hinckley (1936). Star-names and their meanings. pp. 100–101.
- Wehr, Hans (1994). Cowan, J. Milton (ed.). A dictionary of modern written Arabic.
- Davis Jr., G. A. (October 3, 1944). "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names". Popular Astronomy. 52: 13. Bibcode:1944PA.....52....8D.
- Olcott, William Tyler (2004). Star Lore: Myths, Legends, and Facts. Mineola, New York: Dover Publications Inc. pp. 77–78. ISBN 978-0-8021-4877-3.
- Nyoongah, Mudrooroo; Narogin, Mudrooroo (1994). Aboriginal mythology : an A-Z spanning the history of aboriginal mythology from the earliest legends to the present day. London: HarperCollins. p. 5. ISBN 978-1-85538-306-7.
- Hamacher, Duane W.; Frew, David J. (2010). "An Aboriginal Australian Record of the Great Eruption of Eta Carinae". Journal of Astronomical History & Heritage. 13 (3): 220–34. arXiv:1010.4610. Bibcode:2010JAHH...13..220H. doi:10.3724/SP.J.1440-2807.2010.03.06. S2CID 118454721.
- Johnson, Diane (1998). Night skies of aboriginal Australia: a noctuary. Darlington, New South Wales: University of Sydney. pp. 24, 69, 84, 112. Bibcode:1998nsaa.book.....J. ISBN 978-1-86451-356-1.
- Makemson, Maud Worcester (1941). The Morning Star Rises: an account of Polynesian astronomy. New Haven, Connecticut: Yale University Press. p. 199. Bibcode:1941msra.book.....M.
- Makemson 1941, p. 209.
- Makemson 1941, p. 280.
- Makemson 1941, p. 221.
- Makemson 1941, p. 264.
- Makemson 1941, p. 210.
- Makemson 1941, p. 260.
- "Arcturus". Constellation Guide. Retrieved 20 June 2017.
- Hagar, Stansbury (1900). "The Celestial Bear". The Journal of American Folklore. 13 (49): 92–103. doi:10.2307/533799. JSTOR 533799.
- Daghavarian, Nazaret (1903). Ancient Armenian Religions (in Armenian) (PDF). p. 19. Archived (PDF) from the original on 2022-10-09. Retrieved 12 February 2021.
- Plautus. "Rudens". p. prol. 71.
- Lewis, Charlton T.; Short, Charles (1879). "arctūrus". A Latin Dictionary. Oxford: Clarendon Press. Available on the Perseus Digital Library.
- Alan Roberts, Peter; Yeshi, Tulku (2013). "Karandavyuha Sutra Page 45" (PDF). Pacificbuddha. 84000.
- Zimmer, Stefan (February 1, 2006). Die keltischen Wurzeln der Artussage: mit einer vollständigen Übersetzung der ältesten Artuserzählung Culhwch und Olwen (in German). Universitätsverlag. p. 37. ISBN 978-3825351076.
- Zimmer, Stefan (March 2009). "The Name of Arthur – A New Etymology". Journal of Celtic Linguistics. University of Wales Press. 13 (1): 131–136.
- Walter, Philippe (2005). Artù. L'orso e il re (in Italian). Translated by Faccia, M. Edizioni Arkeios. p. 74. ISBN 978-8886495806.
- Johnson, Flint (2002). The British sources of the abduction and Grail romances. University Press of America. pp. 38–39. ISBN 978-0761822189.
- Chambers, Edmund Kerchever (1964). Arthur of Britain. Speculum Historiale. p. 170.
- Tyson, Donald; Freake, James (1993). Three Books of Occult Philosophy. Llewellyn Worldwide. ISBN 978-0-87542-832-1.
- "The opening ceremony of A Century of Progress". Century of Progress World's Fair, 1933-1934. University of Illinois-Chicago. January 2008. Retrieved 2022-08-28.
- Talcott, Rich (July 14, 2014). "Lincoln and the cosmos". Astronomy Magazine. Retrieved 2022-08-28.
Further reading edit
- Harper, Graham M.; et al. (June 2022), "The Wind Temperature and Mass-loss Rate of Arcturus (K1.5 III)", The Astrophysical Journal, 932 (1): 57, Bibcode:2022ApJ...932...57H, doi:10.3847/1538-4357/ac69d6, S2CID 249880096, 57.
- Isidoro-García, L.; et al. (January 2022), "Theoretical lifetimes and Stark broadening parameters for visible-infrared spectral lines of V I in Arcturus", Monthly Notices of the Royal Astronomical Society, 509 (3): 4538–4554, Bibcode:2022MNRAS.509.4538I, doi:10.1093/mnras/stab3301.
- Kushniruk, Iryna; Bensby, Thomas (November 2019), "Disentangling the Arcturus stream", Astronomy & Astrophysics, 631: A47, arXiv:1909.04949, Bibcode:2019A&A...631A..47K, doi:10.1051/0004-6361/201935234, S2CID 202558933, A47.
- Wood, M. P.; et al. (February 2018), "Vanadium Transitions in the Spectrum of Arcturus", The Astrophysical Journal Supplement Series, 234 (2): 25, arXiv:1712.06942, Bibcode:2018ApJS..234...25W, doi:10.3847/1538-4365/aa9a41, S2CID 119356096, 25.
- Küker, M.; Rüdiger, G. (January 2011), "Differential rotation and meridional flow of Arcturus", Astronomische Nachrichten, 332 (1): 83, arXiv:1012.3321, Bibcode:2011AN....332...83K, doi:10.1002/asna.201011483.
- Lacour, S.; et al. (July 2008), "The limb-darkened Arcturus: imaging with the IOTA/IONIC interferometer", Astronomy and Astrophysics, 485 (2): 561–570, arXiv:0804.0192, Bibcode:2008A&A...485..561L, doi:10.1051/0004-6361:200809611, S2CID 18853087.</ref>
- Brown, Kevin I. T.; et al. (June 2008), "Long-Term Spectroscopic Monitoring of Arcturus", The Astrophysical Journal, 679 (2): 1531–1540, Bibcode:2008ApJ...679.1531B, doi:10.1086/587783, S2CID 121170557.
- Tarrant, N. J.; et al. (November 2007), "Asteroseismology of red giants: photometric observations of Arcturus by SMEI", Monthly Notices of the Royal Astronomical Society: Letters, 382 (1): L48–L52, arXiv:0706.3346, Bibcode:2007MNRAS.382L..48T, doi:10.1111/j.1745-3933.2007.00387.x, S2CID 5666311.
- Brown, Kevin I. T. (February 2007), "Long-Term Spectroscopic and Precise Radial Velocity Monitoring of Arcturus", The Publications of the Astronomical Society of the Pacific, 119 (852): 237, Bibcode:2007PASP..119..237B, doi:10.1086/512731, S2CID 121637958.
- Gray, David F.; Brown, Kevin I. T. (August 2006), "The Rotation of Arcturus and Active Longitudes on Giant Stars", The Publications of the Astronomical Society of the Pacific, 118 (846): 1112–1118, Bibcode:2006PASP..118.1112G, doi:10.1086/507077, S2CID 120918694.
- Cohen, Martin; et al. (June 2005), "Far-Infrared and Millimeter Continuum Studies of K Giants: α Bootis and α Tauri", The Astronomical Journal, 129 (6): 2836–2848, arXiv:astro-ph/0502516, Bibcode:2005AJ....129.2836C, doi:10.1086/429887, S2CID 119419198.
- Navarro, Julio F.; et al. (January 2004), "The Extragalactic Origin of the Arcturus Group", The Astrophysical Journal, 601 (1): L43–L46, arXiv:astro-ph/0311107, Bibcode:2004ApJ...601L..43N, doi:10.1086/381751, S2CID 10638792.
- Retter, Alon; et al. (July 2003), "Oscillations in Arcturus from WIRE Photometry", The Astrophysical Journal, 591 (2): L151–L154, arXiv:astro-ph/0306056, Bibcode:2003ApJ...591L.151R, doi:10.1086/377211, S2CID 119083930.
- Ryde, N.; et al. (November 2002), "Detection of Water Vapor in the Photosphere of Arcturus", The Astrophysical Journal, 580 (1): 447–458, arXiv:astro-ph/0207368, Bibcode:2002ApJ...580..447R, doi:10.1086/343040, S2CID 7672420.
- Griffin, R. E. M.; Lynas-Gray, A. E. (June 1999), "The Effective Temperature of Arcturus", The Astronomical Journal, 117 (6): 2998–3006, Bibcode:1999AJ....117.2998G, doi:10.1086/300878, S2CID 120907426.
- Turner, Nils H.; et al. (May 1999), "Adaptive Optics Observations of Arcturus using the Mount Wilson 100 Inch Telescope", The Publications of the Astronomical Society of the Pacific, 111 (759): 556–558, Bibcode:1999PASP..111..556T, doi:10.1086/316353, S2CID 2441153.
- Griffin, R. F. (October 1998), "Arcturus as a double star", The Observatory, 118: 299–301, Bibcode:1998Obs...118..299G.
- Quirrenbach, A.; et al. (August 1996), "Angular diameter and limb darkening of Arcturus.", Astronomy and Astrophysics, 312: 160–166, Bibcode:1996A&A...312..160Q.