NIHAL (Beta Leporis). Lepus (the Hare), lying beneath Orion's feet, consists of third magnitude and fainter stars. Arneb, the Alpha star, is the brightest, and is logically followed by the Beta star, Nihal. The most prominent part of Lepus consists of a pair of distorted boxes lying side-by-side. The name Arneb relates to the Hare itself. Nihal, however, tells us of old Arabic constellations. The left box, made of Arneb, Nihal, and the Gamma and Delta stars, form a figure called al-nihal, meaning (from scholarly work by Kunitzsch and Smart) "the camels beginning to quench their thirst," our Nihal standing in for a quartet of drinking beasts. If nothing else, Nihal shows that the range of constellation lore far exceeds that to which we are usually accustomed. The star itself is rather unusual. Shining at modestly bright third magnitude (2.84), it is, like the Sun, a class G (G5) star, though a bright giant rather than a solar-type dwarf. Its color is very similar to that of the Sun, the temperature (5225 Kelvin) only 555 Kelvin cooler than the solar surface. From its distance of 159 light years, we find that it shines 165 times more brightly than the Sun, from which (with temperature) we deduce a radius 16 times solar. This three solar mass star is in a relatively rare state. Rapidly evolving with a quiet helium core, in less than a million years it will begin to brighten as it prepares to fuse its internal helium to carbon some three or so million years from now (rather like Capella B). Like so many stars, Nihal is double. The companion, only 2.5 seconds of arc away from Nihal proper, has been listed as bright as seventh magnitude and as dim as eleventh. The companion might itself be an eclipsing double (in which one of a pair periodically gets in front of the other), but the divergence in magnitude measure more likely stems from the problem of observing dim stars with bright, nearby companions that overwhelm them. There are three other faint companions in the neighborhood, but they may just lie in the line of sight. Nihal is an X-ray source, which suggests magnetic activity. Although the star's chemical composition is for the most part like that of the Sun, it is considerably enriched in yttrium and the rare earths praseodymium, neodymium, and samarium. Nihal began its life as a star near the class A-class B border a bit hotter than Vega. Many such stars have these odd abundances as a result of chemical separation in their atmospheres, and maybe Nihal has a memory of what it once was.
Written by Jim Kaler. Return to STARS.