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Albireo
(β Cyg, β Cygni, Beta Cyg, Beta Cygni) is the fifth brightest
star in the constellation Cygnus. Although it has the Bayer designation
beta, it is fainter than Gamma Cygni, Delta Cygni, and Epsilon Cygni.
Albireo appears to the naked eye to be a single star of magnitude 3 but
through a telescope, even low magnification views resolve it into a
double star. The brighter yellow star (actually itself a very close
binary system) makes a strikingly beautiful colour contrast with its
fainter blue companion star ensuring that Albireo is one of amateur
astronomers' most cherished summertime observing targets. Approximately
380 light-years (120 pc) away from the Earth, when viewed with the
naked eye, Albireo appears to be a single star. However, in a telescope
it readily resolves into a double star, consisting of Albireo A (amber,
apparent magnitude 3.1), and Albireo B (blue-green, apparent magnitude
5.1.)Separated by 35 seconds of arc, he two components provide one of
the best contrasting double stars in the sky due to their different
colors. It is not known whether the two components are orbiting around
each other in a physical binary system. If they are, their orbital
period is probably at least 100,000 years.
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