SUALOCIN (Alpha Delphini). Stars can come by their names in strange ways.
Moreover, there is a distinct lack of consistency between naming
and brightness, second magnitude Gamma
Cassiopeia having no proper name and the two brighter stars in
Delphinus, the Dolphin, though both of
fourth magnitude, both honored with such names. If they had not
been in such a jewel-like constellation, they probably would have
been ignored. The mysterious names "Sualocin" and its partner
"Rotanev" appeared in the
Palermo star catalogue of 1814. A bit of
detective work by the nineteenth century English astronomer Thomas
Webb finally disclosed that the stars are the reversed Latinized
names of the assistant to the observatory's astronomer Giuseppe
Piazzi, Nicolaus Venator, so honoring him. Though at bright fourth
magnitude (3.77) slightly dimmer than Rotanev, Sualocin received the
constellation's Alpha designation from Bayer. This class B (B9) star,
just over the edge from class A, has a surface temperature of
11,000 Kelvin. Like most B stars, it is spinning rapidly, 160
kilometers per second at its equator (70 times faster than the Sun). Its status is somewhat uncertain, some
observers calling it a hydrogen-fusing main sequence star, others
a subgiant that might just be starting to evolve. At a distance of
240 light years, the star appears to have a luminosity 195 times
that of the Sun. It has been known for some time, however, that
Sualocin has a close companion a fraction of a second of arc away.
Modern measurements with the Hipparcos satellite show the companion
to be about a tenth the brightness of the principal star, revealing
it to be a class A star rather similar to Sirius. The principal component is
therefore a bit less bright, about 175 times solar. The two orbit
each other with a period of 17 years at an average separation of
about 12 astronomical units, a bit farther than Saturn is from the
Sun, the total mass found from the orbit to be 5.8 times solar,
most of (over 3 solar masses) in the main component. Since the
brighter star will die first as a dim white dwarf, the system may
someday appear much as Sirius (with its white dwarf companion) does
today.