In 1610, galileo discovered moons on this planet. what planet was discovered?

Hold up, hee-haw, whoa !  Back it up.

-- When Galileo decided to point his toy telescope at things
in the sky, he discovered moons circling the planet Jupiter.
Right now, in 2016, something like 65 moons of Jupiter are
known.  Galileo saw four of them.  You can see those too, if
you have binoculars and you know how to find Jupiter in the sky.  

-- The Moons aren't "on" Jupiter; they follow orbits around it,
at some considerable distance from it. 

-- Galileo didn't 'discover' Jupiter.  Jupiter is quite visible to
the unaided eye, and has been for several thousand years. 
That's a big part of the reason why Galileo decided to give it
a look-see with his telescope.

Distance^2= yellow line ^2 (see picture) = 30^2 + 49^2so distance = squareroot of (300^2 +49^2)i dont know if this is how to solve it, but i cnt think of another way