Menkalinan lies at the northeast corner of Auriga, immediately to the east of brilliant Capella. Though the third brightest star in the classic pentagon of Auriga, Menkalinan carries the designation β Aur (the second brightest, Elnath, connects Auriga with Taurus, and is more properly known as Beta Tauri.)
Menkalinan's Arabic name means "the shoulder of the rein-holder". Its position helps locate the "solstitial colure," the great circle in the sky that passes through both celestial poles and the summer and winter solstices. It is in remarkable but coincidental alignment along the colure, along with θ, δ, and π Aur.
Properties and Components
Menkalinan is a class A star with a temperature of 9200 K, not very different from Vega or Sirius. From its distance of 82 light years, we calculate a luminosity of 95 times the Sun's, somewhat brighter than a normal class A main sequence star should be.
Careful observation reveals that every 3.96 days, the star undergoes a partial eclipse of about a tenth of a magnitude, showing that it actually consists of two almost identical stars in a tight orbit. Each is about 48 times more luminous than the Sun, and they are separated only about one-fifth the distance between the Sun and Mercury. They may both be subgiants that have begun to brighten as a result of exhausting their core hydrogen fuel. They are so close together that they distort each other through mutual tides; neither component is round.
A faint red dwarf far below naked-eye visibility appears to orbit the pair at least 330 AU away. From it, the bright pair would be just barely separable by eye.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]