Beta Tauri

Elnath, β Tau

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] Because it is on the boundary of Taurus and Auriga, it also has the redundant Bayer designation Gamma Aurigae (γ Aur), which today is rarely used. The star has the traditional name Elnath—a reference to "the butting" of the bull's horns.

Properties

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.^[7] 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.^[8]

Double star

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.^[9][10]

Etymology

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.^[11] Consequently, β Tauri itself is known as 五車五 (Wǔ Ju wǔ; English: Fifth of the Five Chariots.)^[12]

See also

• Lists of stars in the constellation Taurus
• Class B Stars
• Beta Tauri in fiction

References

External links

• Jim Kaler's Stars:Elnath
• Image of Elnath from APOD

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