Beta Tauri

Nomenclature

Beta Tauri is the star's Bayer designation. Ptolemy considered the star to be shared by Auriga, and Johann Bayer assigned it a designation in both constellations: Beta Tauri and Gamma Aurigae (γ Aur). When the modern constellation boundaries were fixed in 1930, the latter designation dropped from use.

The traditional name Elnath, variously El Nath or Alnath, 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 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 Elnath for this star.

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

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. 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 the Milky Way Galaxy a few degrees west of the galactic anticenter, Elnath heralds a rich collection of nebulae and star clusters. Relative to the Sun, β Tauri is notable for a high abundance of manganese, but little calcium and magnesium. 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 was 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.

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.