Astronomers measure the brightness of stars, planets and other night sky objects using a scale called magnitude. The lower the magnitude number an object has, the brighter it shines. (Objects with negative numbers are exceptionally bright.)
Here's a look at the brightest stars in the night (and day) sky based on their "apparent magnitude," which is how bright they appear from Earth.
FIRST STOP: Achernar
NEXT: Rigil Kentaurus
NEXT: The Sun