Here are some cool astronomy facts. Throughout this page there will be links to pages that have whole pages dedicated to basically that one fact I found. I can't really fit that on this page so... Enjoy! And learn something new I hope!
Scientists believe that we only see about 4% of the universe, the rest is dark matter and dark energy which are invisible to use but we know must be their because the universe is expanding (more here).
Neutron stars are so dense (from going supernova) one sugar cube of its material would have more mass then a mountain (quick introduction on neutron stars here).
Galileo Galilei is often credited with inventing the telescope. Historians now believe that that the Dutch eyeglass maker Johannes Lippershey invented it. Galileo probably was the first to use it to look at the heavens.
Black holes are so dense that even light can not escape. Though there is a situation, called the Hawking radiation, that says that light may be able to escape (more here).
Distant stars and galaxies are so far away from us the light we are seeing of them is hundreds, thousands, even millions years old, it takes that long for light to travel that far (every time I read this it's amazing).
The first recorded sighting of a supernova explosion was in 1054 C.E. (A.D.). Chinese and Arab astronomers noted that the explosion was so bright it was visible during the day and lit up the sky for months. The remnants of the explosion are now known as the Crab Nebula (more here).
Even though Mercury is the closest planet to the sun it can reach -280 degrees F. This is because Mercury has no atmosphere to trap heat, so the dark side of Mercury is very, very cold (more on Mercury here).
Saturn's rings are flatter then a sheet of paper (more on Saturn here).
The perihelion is were a planet, astroid or comet where it is closest to the sun, whereas an aphelion is were a planet, astroid or comet is farthest away from the sun. Earth's perihelion occurs around the beginning of January and aphelion around the beginning of July (specific dates here up to 2020).
On January 1st, 1801 Giuseppe Piazzi discovered Ceres, the first asteroid. Now a spaceship, called Dawn, is exploring two asteroids Ceres and Vesta (NASA website for Dawn here).
Light from the edge of the sun takes over 2 seconds longer to reach us then light from the middle. If the sun suddenly disappeared (and didn't destroy us first) we wouldn't see a lack of light for 8 minutes (more on the sun here).