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.
MENKENT
(Theta Centauri). Centaurus isdominated by its two brightest stars, Rigel Kentaurus (Alpha Centauri, third brighteststar in the sky and the nearest star to the Earth) and firstmagnitude Hadar (Beta Centauri). Thoughthese two shine brilliantly to the lucky residents of the southernhemisphere, neither is visible from mid-northern latitudes, so ifthose that live there wish to know Centaurus, they must begin withthe third brightest star in the constellation, Menkent, to which isassigned the rather lowly letter Greek letter Theta (Gamma Centaurirather oddly coming in second). The name comes from an Arabic wordfor "shoulder" (of the Centaur), to which is attached the Latinabbreviation for "Kentaurus" for Centaur, tying Menkent back to theconstellation's luminary, Rigil Kentaurus. Menkent, at mid-secondmagnitude (2.06) is but four percent fainter to the eye than Polaris. Much closer than Polaris,however, only 61 light years away, it is intrinsically much lessluminous. At the warm end of class K (K0), the star is a near-clone of the northern hemisphere's Pollux, just fainter to the eye than Polluxbecause it is 80 percent more distant. Menkent, with no known oreven suspected companions, is about as pure a sample of its classyou can come by. From its 4780 Kelvin surface, this yellow-orangestar radiates at a luminosity 60 times that of the Sun, the star's radius 11 times solar. Wellalong in its evolution, Menkent is now fusing helium into carbonand oxygen in its deep core. The star's only offbeat property isits rather high "proper motion," its speed across the line ofsight. Approaching us at only one kilometer per second, it isspeeding past us at 65 kilometers per second, about twice "normal,"suggesting that the star really belongs to the outer part of theGalaxy's disk and is only visiting the solar neighborhood.