What is the brightest star in the night sky?
Sirius, in the constellation Canis Major, is the brightest star in the night sky. It is about 8.6 light-years away and is also called the Dog Star.
Sirius shines brightly because it is both fairly close and much more luminous than the Sun, about 25 times brighter in total light. It is actually a pair of stars: Sirius A, which we see, and a faint white dwarf companion, Sirius B.
In ancient Egypt, the first appearance of Sirius before sunrise each summer signaled the coming flood of the Nile. The hot summer days around that time became known as the dog days, after the Dog Star.
Brighter objects
Some planets outshine Sirius. Venus is the brightest natural object in the night sky after the Moon, and Jupiter and sometimes Mars can also appear brighter. The second-brightest star is Canopus, visible mainly from the Southern Hemisphere.
Astronomers measure brightness with a scale called magnitude, where smaller numbers mean brighter objects. Sirius has a magnitude of about −1.46, while the faintest stars visible to the naked eye are around +6.
Did You Know?
Sirius appears to twinkle in different colors when it is low in the sky, because Earth's atmosphere bends its light unevenly.