The ancient Greek astronomers divided stars according to their brightness. Till the invention of the telescope, the division was only of six classes or magnitudes. Stars of the first magnitude were the brightest, and those of the sixth were the faintest.
Since the invention of the telescope, the division has gone to more than twenty. There are about 22 stars of the first magnitude, that is, the brightest stars. The brightest star of all is Sirius, which has a magnitude of –1.6, making it over 1,000 times brighter than the faintest star we can see with the naked eye. The numbers of stars increase as we go down in magnitude. There are about 1,000,000,000 stars of the 20th magnitude.
Below Sirius info from Wikipedia (Read More):-
Sirius is the brightest star in the night sky with a visual apparent magnitude of −1.46, almost twice as bright as Canopus, the next brightest star. The name Sirius is derived from the Ancient Greek Σείριος.[19] The star has the Bayer designation α Canis Majoris (α CMa, or Alpha Canis Majoris). What the naked eye perceives as a single star is actually a binary star system, consisting of a white main sequence star of spectral type A1V, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B.
http://en.wikipedia.org/wiki/Sirius
