This star has two
Bayer designations: β Tauri (Latinised to Beta Tauri) and γ Aurigae (Latinised to Gamma Aurigae).
Ptolemy considered the star to be shared by
Auriga, and
Johann Bayer assigned it a designation in both constellations. When the modern constellation boundaries were fixed in 1930, the designation γ Aurigae largely dropped from use.[12]
The traditional name Elnath, variously El Nath or Alnath, comes from the Arabic word النطحan-naţħ, meaning "the butting" (i.e. the bull's horns). As in many other Arabic star names, the article ال is transliterated literally as el, yet overwhelmingly in Arabic pronunciation it is assimilated to the n, meaning it is omitted. In 2016, the
International Astronomical Union organized a
Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[14] included a table of the first two batches of names approved by the WGSN; which included Elnath for this star.[15]
The
absolute magnitude of Beta Tauri is −1.34, similar to another star in Taurus,
Maia in the
Pleiadesstar cluster. Like Maia, β Tauri is a
B-classgiant with a luminosity 700 times solar (L☉).[18] It has evolved to become a giant star, larger and cooler than when it was on the
main sequence.[19]
However, being approximately 130
light-years distant compared to Maia's estimated 360 light-years, β Tauri ranks as the second-brightest star in the constellation.
It is a
mercury-manganese star, a type of non-magnetic chemically peculiar star with unusually large signatures of some heavy elements in its
spectrum.[11] Relative to the
Sun, β Tauri is notable for a high abundance of
manganese, but little
calcium and
magnesium.[18][20] However, the lack of strong
mercury signatures, together with notably high levels of
silicon and
chromium, have led some authors to give other classifications, including as a "SrCrEu star" or even an
Ap star.[21][22] Its
limb-darkened angular diameter has been measured at 1.090±0.076
mas. At a distance of 41.1 pc, this corresponds to a linear radius of 4.82±0.34 R☉.[9]
At the southern edge of the narrow plane of the
Milky Way Galaxy a few degrees west of the
galactic anticenter, β Tauri figures (appears) as a foreground object south of many
nebulae and
star clusters such as
M36,
M37, and
M38.[23] It is 5.39 degrees north of the
ecliptic, still few enough to be occultable by the
Moon. Such occultations occur when the Moon's
ascending node is near the
March equinox, as in 2007. Most are visible only in the
Southern Hemisphere, because the star is at the northern edge of the lunar occultation zone – but rarely as far north as southern
California.[24]
Companions
A faint star is, angularly from our viewpoint, close enough for astronomers to consider, and guides to mention, the pair as a
double star. This visual companion, BD+28°795B, has a
position angle of 239 degrees and is separated from the main star by 33.4
arcseconds (″).[25][26] Six angularly closer, even fainter stars have been found in a search for brown dwarf and planetary companions – all considered background objects.[27]
A very close companion was reported from
lunar occultation measurements at a distance of 0.1
″, but not confirmed by other observers.
Radial velocity measurements indicate that Beta Tauri is a single-lined
spectroscopic binary, but there is no published information about the companion or orbit.[28][9]
^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.
ISBN978-1-931559-44-7.
^Evans, D. S (1967). "The Revision of the General Catalogue of Radial Velocities". Determination of Radial Velocities and Their Applications. 30: 57.
Bibcode:
1967IAUS...30...57E.