Space is a really
big place. There are billions of galaxies and each one has billions of stars.
Recent discoveries suggest that planetary systems are the rule and not the
exception around stars. So the number of moons in space is uncountable.
I suspect you meant
to ask how many moons there are in our solar system. When I was young, a long
time ago, books about the solar system gave precise numbers for the moons of
each planet. Then came the Pioneer and Voyager spacecraft and vastly better
telescopes. The answer is no one knows. It seems every time we a get closer look
at the distant planets, like Saturn, Uranus, or Neptune, we discover they have
more moons than we previously thought. Even Pluto is now known to have at least
two moons.
This Friday (March
6, 2015) the dwarf planet Ceres, the largest body in the Asteroid Belt, will
get a new moon, or at least a satellite. NASA’s Dawn spacecraft will slip into
orbit around this body for a visit.