Alioth
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Ursa Major |
Right ascension | 12h 54m 01.74959s[1] |
Declination | +55° 57′ 35.3627″[1] |
Apparent magnitude (V) | 1.77[2] |
Characteristics | |
Spectral type | A1III-IVp kB9 |
U−B color index | +0.02[2] |
B−V color index | −0.02[2] |
Variable type | |
Astrometry | |
Radial velocity (Rv) | −9.3[3] km/s |
Proper motion ( | RA: +111.91 mas/yr[1] Dec.: −8.24 mas/yr[1] |
Parallax ( | 39.51 ± 0.20 mas[1] |
Distance | 82.6 ± 0.4 ly (25.3 ± 0.1 pc) |
Absolute magnitude (MV) | −0.2[4] |
Details | |
Mass | 2.91[5] M☉ |
Radius | 4.29+0.19 −0.21[6] R☉ |
Luminosity | 104.4±9.3[6] L☉ |
Surface gravity (log g) | 3.59[6] cgs |
Temperature | 8,908±24[6] K |
Metallicity [Fe/H] | +0.00[4] dex |
Rotational velocity (v sin i) | 33[7] km/s |
Age | 300[8] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Alioth /ˈæliɒ
It is the star in the tail of the bear closest to its body, and thus the star in the handle of the Big Dipper (or Plough) closest to the bowl. It is also a member of the large and diffuse Ursa Major moving group. Historically, the star was frequently used in celestial navigation in the maritime trade, because it is listed as one of the 57 navigational stars.[1]
Physical characteristics
[edit]![](https://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Sidney_Hall_-_Urania%27s_Mirror_-_Ursa_Major.jpg/200px-Sidney_Hall_-_Urania%27s_Mirror_-_Ursa_Major.jpg)
![](https://upload.wikimedia.org/wikipedia/commons/thumb/3/3f/EpsUMaLightCurve.png/220px-EpsUMaLightCurve.png)
According to Hipparcos, Epsilon Ursae Majoris is 81 light-years (25 parsecs) from the Sun. Its spectral type is A1p; the "p" stands for peculiar, as its spectrum is characteristic of an
Epsilon Ursae Majoris's rotational and magnetic poles are at almost 90 degrees to one another. Darker (denser) regions of chromium form a band at right angles to the equator.
It has long been suspected that Epsilon Ursae Majoris is a spectroscopic binary, possibly with more than one companion.[12] A more recent study suggests Epsilon Ursae Majoris's 5.1-day variation may be due to a substellar object of about 14.7 Jupiter masses in an eccentric orbit (e=0.5) with an average separation of 0.055 astronomical units.[13] It is now thought that the 5.1-day period is the rotation period of the star, and no companions have been detected using the most modern equipment.[14] A 2023 study did not any evidence of a companion star (after observation of Alioth with the Navy Precision Optical Interferometer), although further observations might detect (or not) a companion.[6]
Epsilon Ursae Majoris has a relatively weak magnetic field, 15 times weaker than
Name and etymology
[edit]The traditional name Alioth comes from the Arabic alyat al-hamal ("the sheep's fat tail"). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[16] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[17] included a table of the first two batches of names approved by the WGSN; which included Alioth for this star.
This star was known to the Hindus as Añgiras, one of the Seven Rishis.[18]
In Chinese,
Namesakes
[edit]The United States Navy's Crater class cargo ship USS Allioth (AK-109) was named after the star.
See also
[edit]References
[edit]- ^ a b c d van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600
- ^ a b c Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
- ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from I
AU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E - ^ a b Tektunali, H. G. (June 1981), "The spectrum of the CR star Epsilon Ursae Majoris", Astrophysics and Space Science, 77 (1): 41–58, Bibcode:1981Ap&SS..77...41T, doi:10.1007/BF00648756, S2CID 122817347
- ^ Shaya, Ed J.; Olling, Rob P. (January 2011), "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue", The Astrophysical Journal Supplement, 192 (1): 2, arXiv:1007.0425, Bibcode:2011ApJS..192....2S, doi:10.1088/0067-0049/192/1/2, S2CID 119226823
- ^ a b c d e Baines, Ellyn K.; Clark, James H., III; Schmitt, Henrique R.; Stone, Jordan M.; von Braun, Kaspar (2023-12-01). "33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble". The Astronomical Journal. 166 (6): 268. Bibcode:2023AJ....166..268B. doi:10.3847/1538-3881/ad08be. ISSN 0004-6256.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393 (3): 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943, S2CID 14070763
- ^ Nakajima, Tadashi; Morino, Jun-Ichi (2012). "Potential Members of Stellar Kinematic Groups within 30 pc of the Sun". The Astronomical Journal. 143 (1): 2. Bibcode:2012AJ....143....2N. doi:10.1088/0004-6256/143/1/2.
- ^ 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, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
- ^ "I
AU Catalog of Star Names". Retrieved 28 July 2016. - ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
- ^ Morgan, B. L.; Beddoes, D. R.; Scaddan, R. J.; Dainty, J. C. (1978). "Observations of binary stars by speckle interferometry – I". Monthly Notices of the Royal Astronomical Society. 183 (4): 701–710. Bibcode:1978MNRAS.183..701M. doi:10.1093/mnras/183.4.701.
- ^ Sokolov, N. A. (March 2008), "Radial velocity study of the chemically peculiar star ɛ Ursae Majoris", Monthly Notices of the Royal Astronomical Society: Letters, 385 (1): L1–L4, arXiv:0904.3562, Bibcode:2008MNRAS.385L...1S, doi:10.1111/j.1745-3933.2008.00419.x, S2CID 17104356.
- ^ Shulyak, D.; Paladini, C.; Causi, G. Li; Perraut, K.; Kochukhov, O. (2014). "Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities". Monthly Notices of the Royal Astronomical Society. 443 (2): 1629. arXiv:1406.6093. Bibcode:2014MNRAS.443.1629S. doi:10.1093/mnras/stu1259. S2CID 96452769.
- ^ Kochukhov, O.; Shultz, M.; Neiner, C. (2019). "Magnetic field topologies of the bright, weak-field Ap stars
θ Aurigae and ∊ Ursae Majoris". Astronomy and Astrophysics. 621: A47. arXiv:1811.04928. Bibcode:2019A&A...621A..47K. doi:10.1051/0004-6361/201834279. S2CID 119070948. - ^ "I
AU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. - ^ "Bulletin of the I
AU Working Group on Star Names, No. 1" (PDF). Archived (PDF) from the original on 2022-10-09. Retrieved 28 July 2016. - ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 438. ISBN 0-486-21079-0. Retrieved 2012-09-04.
- ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy)
天文 教育 資 訊網 2006年 6月 15日
- ^
This article incorporates text from a publication now in the public domain: Chambers, Ephraim, ed. (1728). "Allioth". Cyclopædia, or an Universal Dictionary of Arts and Sciences (1st ed.). James and John Knapton, et al.