Thanks to James B. Kaler. These contents are the property of the author and are reproduced from original without the author's express consent because of fair use and valid educational purposes.
Beautifully shaped Auriga, the Charioteer, rides high in northern winter skies, dominated by brilliant Capella at the northwestern corner of the prominent pentagon the makes the figure. Almost immediately to the east lies a mid-second magnitude star, Menkalinan (Men-KAL-in-an), at the northeast corner, the Arabic name meaning "the shoulder of the rein-holder." Though the third brightest star in the classic pentagon, Menkalinan carries Auriga's "Beta" designation. The second brightest, Elnath, close to first magnitude, connects Auriga with Taurus, and though it has the formal name Gamma Aurigae, is more properly known as Beta Tauri, technically leaving Menkalinan second brightest in Auriga. As Polaris locates the north pole and Mintaka in Orion's Belt the celestial equator, Menkalinan locates the "solstitial colure," the great circle in the sky that passes through both celestial poles and the summer and winter solstices. Menkalinan is a mere half-minute of arc (an angle less than the eye can see) off the colure. Immediately south lies Theta Aurigae, which is even closer, a quarter of a minute away. A line passed through these stars to the south points at Betelgeuse in Orion, the summer solstice (the location of the Sun on the first day of summer) lying in Gemini about half way between Theta and Betelgeuse. Menkalinan is a class A star with a temperature of 9200 Kelvin, not very much different from Vega or Sirius. From its distance of 82 light years, we calculate a luminosity 95 times that of the Sun, somewhat brighter than a normal "A 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 about 48 times more luminous than the Sun separated only about one-fifth the distance between the Sun and Mercury. They may both be "subgiants" that have begun to change and brighten as a result of exhaustion of their core hydrogen fuel. They are so close that they distort each other through mutual tides, neither of them round. A faint red dwarf far below naked-eye vision appears to orbit the pair at least 330 Earth-Sun distances away, from which the bright pair would be just barely separable by eye.