BETA EQU (Beta Equulei). Among the only reasons to tout this star
is Bayer's Beta designation, as we try to accommodate all the Beta
stars. As is fairly common, the constellation of Equuleus, the Little Horse, is dominated by the Alpha
star, fourth magnitude Kitalpha, while
Beta does not come up to par. Number two is Delta Equ, followed by Gamma, and then in
fourth place, up comes fifth magnitude (5.16) Beta. If you thought
(if anybody thinks to think it) that Beta
Piscis Austrini was neglected, try this one, with a sad 27
professional references over the past century or so. On the
surface, it's just another class A (A3) dwarf, yet one with its own
small interest. At roughly 9000 Kelvin, Beta Equulei shines at us
from a distance of 101 light years (give or take 3) with a
luminosity of 75 times that of the Sun --
nice and bright for its class. That gives us a radius of 3.6 solar
and (given an equatorial rotation velocity of at least 49
kilometers per second) a rotation period under four days. The mass
falls between 2.4 and 2.5 times that of the Sun depending on the
exact state of evolution, which in any case is near the end of the
hydrogen-fusing line, really rendering the star a subgiant, the age
about 600 million years. In spite of the pathetic number of
references, Beta Equ has two things to recommend it. First, like
Vega and Fomalhaut, it's surrounded by a dusty
disk that by itself suggests planets (though
none have been found). Second it has a swarm of faint (12th-14th
magnitude) companions, Beta-
B through E, whose separations range from 39 seconds of arc to 94
seconds away. All of them, however, are moving too fast relative
to Beta-A, and are thus clearly just line-of-sight coincidences.
Curiously the CD pair may indeed be a real binary, though little is
known, and nobody seems to care -- in line with Beta Equulei
proper.
Written by Jim Kaler 12/18/09. Return to STARS.