The stars on the celestial sphere are named in several different ways. As a result, the brighter stars may have more than one name. We give a brief overview of naming stars here.
Most of the brighter stars in the sky have common names that are of historical
and mythological significance. For example, the bright red star in the
shoulder region of the constellation Orion (the Hunter) is called Betelgeuse,
which comes from Arabic and means (roughly) "the armpit of the mighty one"
(see adjacent figure).
The brightest star in Orion is a blue-white star called Rigel that is situated
at the opposite corner of the constellation from Betelgeuse (adjacent figure). As another example, the brightest star in the constellation Cygnus (the Swan) is situated near the aft portion of the beast and is called Deneb, which is also Arabic in origin and means "the tail of the hen".
Common names are fine for a few bright stars, but we need a more systematic
method to name all the stars that we see. One
more systematic method is the Bayer system,
which names the brighter stars by assigning a constellation (using the Latin
possessive of the name) and a greek letter
(Alpha, Beta, Gamma, Delta, Epsilon, . . .) in an approximate
order of decreasing brightness
for stars in the constellation. The adjacent figure illustrates for Orion.
Betelgeuse is also called Alpha-Orionis and
Rigel is
called Beta Orionis in the Bayer system.
The ordering of stars by brightness in the classical Bayer system is only approximate. For example, Rigel (Beta Orionis) is actually slightly brighter than Betelgeuse (Alpha Orionis), and Kappa Orionis is considerably brighter than the position of Kappa in the Greek alphabet would suggest.
As a final example, the brightest star in the nighttime sky is Sirius,
which is in the constellation Canis Major and is termed Alpha Canis
Majoris in the Bayer naming system. Here is a list of 70 of the
brighter stars, including common names, Bayer names,
positions on the celestial sphere, and
spectral class.