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.