Hadar (Beta Centauri)
The second brightest star in the constellation Centaurus
and the eleventh brightest star in the sky; the origin of its name is unclear,
though its alternative name Agena means the "knee" of the Centaur.
|Hadar (r) and Alpha Centauri (l)
Photo: Southern Astronomical Society
Hadar consists of a pair of almost identical, giant B
stars, each some 55,000 times more luminous and 15 times more massive
than the Sun separated by about 3 AU with an orbital period of just under
a year. A fourth magnitude sibling, Hadar-B, 1.3 arc-sec away, is difficult
to see and study because of the brightness difference but, as a B-type dwarf,
is an impressive star in its own right, with a mass of 5 solar masses and
a luminosity 1,500 times that of the Sun. Hadar-B orbits the main pair at
a minimum distance of 210 AU with a period of at least 600 years. The twins
that make up Hadar-A are some 12 million years old and due to quickly expand
to become red supergiants prior to exploding as supernovae. One of the twins
is also a Beta Cephei star, subtly
varying with multiple periods of less than a day.
||R.A. 14h 03m 49.4s,
Dec. -60° 22' 23"