Good question! Yes, the sun is really a
star. The sun is about 4.6 billion years old,
and it's known as a "main sequence" star.
That means that it is vigorously converting
hydrogen to helium and releasing a lot of energy
(some of that energy heats the surface of the
Earth). The sun is not the biggest one in the
Universe, but it's not the smallest either! The
smallest stars in the Universe are called "red
dwarfs". Some red dwarfs are only 1/10 as massive
as the sun (NASA). The biggest stars are known as
According to the NASA website, some
hypergiants are more than 100 times as massive as
the sun, and much brighter! I've included links to
a couple of cool NASA resources. The first link
below is for a NASA webpage that has a really neat
video that compares the size of planets and stars.
The second link is to a page with a lot of
interesting facts about the sun.