Simply because it is identical in basic chemistry and physics to every other observable main sequence star of it's type in the universe. If it looks like a duck, quacks like a duck, and walks like a duck - odds are: It's a Duck!
No, The sun is seen as a sun and not a star. Our sun is a star.
The Sun is a star.
The Sun is a star.
The Sun is a star.
Our Sun is a star
The Sun is a Star
Our sun is actually a small star, tons of stars are way bigger than our sun. One. Each star is a sun.
Nope. The sun is considered a star.
The sun is a star. A star is a sun.
Yes, the sun is a star.
The sun is a star.
The sun is a star!