Beta Tauri

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Elnath, β Tau
Taurus constellation map.svg
Elnath is the β star in Taurus (map: top left).
Observation data
Epoch J2000      Equinox J2000
Constellation Taurus
Right ascension 05h 26m 17.5134s[1]
Declination 28° 36′ 27.494″[1]
Apparent magnitude (V) 1.68[1]
Characteristics
Spectral type B7III[1]
U−B color index -0.49[1]
B−V color index -0.13[1]
Variable type None
Astrometry
Radial velocity (Rv) 9.2[1] km/s
Proper motion (μ) RA: 23.28[1] mas/yr
Dec.: -174.22[1] mas/yr
Parallax (π) 24.89 ± 0.88[1] mas
Distance 131 ± 5 ly
(40 ± 1 pc)
Absolute magnitude (MV) -1.34
Details
Mass 5.0 ± 0.1[2] M
Radius 4.2[3] R
Luminosity 700[4] L
Temperature 13,824 ± 475[3] K
Metallicity [Fe/H] -0.10[1][5] dex
Rotational velocity (v sin i) 82[1][6] km/s
Age 100 ± 10[2] Myr
Other designations
Elnath, El Nath, Alnath, β Tau, γ Aur, 112 Tau, BD +28°795, BD+23 541, CCDM 05263+2836, FK5 202, HD 35497, HR 1791, HIP 25428, SAO 77168, GC 6681.
Database references
SIMBAD data

Beta Tauri (β Tau, β Tauri) is the second brightest star in the constellation Taurus, with an apparent magnitude of 1.68.[1] Ptolemy considered Beta Tauri to be shared by Auriga, and Bayer assigned it a designation in both constellations: Beta Tauri (β Tau) and Gamma Aurigae (γ Aur). When the modern constellation boundaries were fixed in 1930, the latter designation dropped from use.[7] The star has the traditional name Elnath—a reference to "the butting" of the bull's horns.

Properties[edit]

Elnath's absolute magnitude is -1.34, similar to another Taurean star, Maia in the Pleiadian star cluster. Like Maia, Elnath is a B class giant with a luminosity 700 times solar.[4] However being approximately 130 light years distant compared to Maia's estimated 360 light years, Elnath ranks as the second brightest star in the constellation.

Uniquely positioned along the plane of our Milky Way Galaxy a few degrees west of the galactic anticenter, Elnath heralds a rich collection of nebulae and star clusters.[8] Relative to our Sun, β Tauri is notable for a high abundance of manganese, but little calcium and magnesium.[4][5] This star has begun to evolve away from the main sequence.

This star can be occulted by the moon. Such occultations occur when the moon's ascending node is near the vernal equinox, as is the case in 2007. Most occultations are visible only in parts of the Southern Hemisphere, because the star lies at the northern edge of the lunar occultation zone. Rarely, it may be occulted as far north as southern California.[9]

Double star[edit]

There is a faint star that appears close enough to Elnath for astronomers to consider it a double star. Its visual companion, known as BD+28 795B, has a PA of 239 degrees and is separated from the main star by 33.4 arcseconds.[10][11]

Etymology[edit]

Beta Tauri has the traditional name Elnath, El Nath, or Alnath, which comes from the Arabic word النطح an-naţħ, meaning "the butting" (i.e. the bull's horns). As in many other (but not all) Arabic star names, the article ال is transliterated literally as el, despite the fact that in Arabic pronunciation it is assimilated to the following n; it can also be omitted: Nath.

In Chinese, 五車 (Wǔ Ju), meaning Five Chariots, refers to an asterism consisting of β Tauri, ι Aurigae, Capella, β Aurigae and θ Aurigae.[12] Consequently, β Tauri itself is known as 五車五 (Wǔ Ju wǔ; English: Fifth of the Five Chariots.)[13]

See also[edit]

References[edit]

  1. ^ a b c d e f g h i j k l m "SIMBAD query result: ELNATH -- Star in double system". Centre de Données astronomiques de Strasbourg. Retrieved 2010-03-07. 
  2. ^ a b Janson, Markus et al. (August 2011), "High-contrast Imaging Search for Planets and Brown Dwarfs around the Most Massive Stars in the Solar Neighborhood", The Astrophysical Journal 736 (2): 89, arXiv:1105.2577, Bibcode:2011ApJ...736...89J, doi:10.1088/0004-637X/736/2/89 
  3. ^ a b Underhill, A. B. et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601 
  4. ^ a b c Kaler, James B., ELNATH (Beta Tauri), University of Illinois, retrieved 2010-03-07 
  5. ^ a b Heacox, W. D. (1979). "Chemical abundances in Hg-Mn stars". Astrophysical Journal Supplement Series 41: 675. Bibcode:1979ApJS...41..675H. doi:10.1086/190637. 
  6. ^ Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contr. Oss. Astrof. Padova in Asiago 239. Bibcode:1970CoAsi.239....1B. 
  7. ^ Bayer’s Uranometria and Bayer letters
  8. ^ "Deep Auriga". Today's Astronomy Picture of the Day. 2010-03-05. Retrieved 2010-03-07. 
  9. ^ Abrams Planetarium - Skywatcher's Diary
  10. ^ "CCDM (Catalog of Components of Double & Multiple stars (Dommanget+ 2002)". VizieR. Centre de Données astronomiques de Strasbourg. Retrieved 2010-03-07. 
  11. ^ "Al Nath". Alcyone Bright Star Catalogue. Retrieved 2010-03-07. 
  12. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  13. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.

External links[edit]

Coordinates: Sky map 05h 26m 17.5134s, +28° 36′ 27.494″