Is sun the brightest star

Answer 1

The brightness of a star is usually referred to as its magnitude. Every star has two magnitudes. The apparent magnitude is how bright it appears to us here on earth. The absolute magnitude is the apparent magnitude that the star would have, if it were viewed from a standard distance. The apparent magnitude of our sun is vastly greater than that of any other celestial object. In terms of absolute magnitude, our sun can't begin to compare with some of the big bright stars in the universe.

Answer 2

As brightness is a function of a stars luminosity as observed from Earth, the Sun is most certainly the brightest star.