If you're talking about apparent brightness (how bright a star appears from Earth), then the answer is Sirius. It's a binary star system located in the constellation Canis Major.
However, if you're talking about absolute brightness (how much light a star actually emits), then the answer is much more complicated. There are many stars that are much brighter than Sirius, but they are much farther away from us and therefore appear dimmer.
Here are some of the brightest stars in terms of absolute brightness:
* Rigel: A blue supergiant in the constellation Orion, about 85 times brighter than the sun.
* Deneb: A white supergiant in the constellation Cygnus, about 200,000 times brighter than the sun.
* Betelgeuse: A red supergiant in the constellation Orion, about 100,000 times brighter than the sun.
So, the answer to your question depends on what you're looking for. For the brightest star in the night sky as seen from Earth, the answer is Sirius. But for the most luminous stars in the universe, the answer is much more complex!
