Lambda Tauri

From Wikipedia, the free encyclopedia

**λ Tauri**
Observation data Equinox J2000.0
Constellation	Taurus
Right ascension	04^h 00^m 40.8^s
Declination	+12° 29' 25"
Apparent magnitude (V)	+3.41
Distance	370 ± 42 ly (114 ± 13 pc)
Spectral type	B3V+A4IV
Other designations
Elthor, 35 Tauri, HR 1239 HD 25204, BD+12 539, FK5 150, HIP 18724, SAO 93719, GC 4805

Lambda Tauri (λ Tau / λ Tauri) is a triple star system in the constellation Taurus. It has the traditional name Elthor (Althor, Althaur, Al Thaur), which is Arabic for "The Bull", derived from the title Ath-Thawr Ath-Thurayya (‏الثور الثريا), meaning "The Bull of the Pleiades".

The primary component, Lambda Tauri A, is a blue-white B-type main sequence dwarf with a mean apparent magnitude of +3.41. It has a luminosity of about 4,000 times that of the Sun and a radius of 6.6 times solar. The companion is a white A-type subgiant of 5.5 solar radii and 95 solar luminosities. They orbit around a common centre of gravity once every 3.95 days. The spatial separation between these two stars is measured at 0.1 astronomical unit.

Because the system is an eclipsing binary its brightness varies from magnitude +3.37 to +3.91 as first one star and then the other pass in front of its companion. The system has a third, dimmer star with an orbital period of 33 days. The Lambda Tauri system is approximately 370 light years from Earth.