Stargazers might often believe that Polaris, more commonly known as the North Star, is the brightest in the sky.
The star is certainly helpful for navigating in the wilderness and certainly stands out. (Runaway slaves used to identify the North Star by first finding the Big Dipper, which is directly across from it. The star gave its name to Fredrick Douglass's antislavery newspaper.)
But Polaris is usually ranked as about the 50th brightest star seen from Earth. Sirius, the "Dog Star" of the Canis Major constellation, takes the cake. The star is close to Orion's belt, and for middle to Northern latitudes it's best seen during the winter in the southern part of the sky.
Scientists measure the brightness of stars in magnitudes of one to six. The lower the magnitude, the brighter the star. But remember that apparent brightness is only how bright a star appears to us on Earth, and is completely different from a star's luminosity – the amount of energy a star emits. The most luminous star is harder to determine because astronomers would have to scour the whole Universe. In 2004, astronomers discovered LBV 1806-20, what they believe to be the universe's most luminous star discovered yet.
