Sirius is not the biggest star in the night sky. It's actually just a medium-sized star. The reason it appears so bright is due to its proximity to Earth.

Here's the breakdown:

* Apparent Magnitude: Sirius has an apparent magnitude of -1.46, making it the brightest star in our night sky. Apparent magnitude is a measure of how bright a star appears from Earth.

* Absolute Magnitude: However, Sirius's absolute magnitude, which measures its true brightness, is only +1.42. This means it's actually a fairly average-sized star.

* Distance: Sirius is located only 8.6 light-years away from Earth, making it one of the closest stars to our solar system. This proximity is the primary reason it appears so bright.

In essence, Sirius is a relatively small star that is incredibly close to us, giving it the illusion of being the largest in the night sky.