Maybe you were taken in from stories of a long time ago, in a galaxy far, far away ... Or maybe you desired to boldly go where no one has gone before. When you look up at the sky on a clear night, you'll see endless stars, our moon, maybe another planet shining back at you. Maybe you became interested in celestial bodies when you first found The Big Dipper, which is part of a constellation called Ursa Major. Or when you saw the three brightest stars in Orion's Belt: Rigel, Betelgeuse, and Bellatrix.
Scientists believe our solar system, which is called simply the Solar System, was formed when a giant cloud of dust and gas collapsed under the weight of its own gravity. And, when doing so, it began moving in a big circle -- creating and then spinning around a small star that would eventually become our sun. The galaxies, planets (including Earth) and other objects we see (and don't yet see) in our solar system, including dwarf (minor) planets, moons, comets and asteroids (and leftover dust and gas), were also formed in this event. And objects still unknown. For instance, did you know scientists think there could be a giant but undiscovered planet lurking around Neptune?
And there's more in our solar system than just that -- in fact, just spinning around our own planet there's an estimated 500,000 bits of orbital debris measuring between one and 10 centimeters in diameter and an additional 21,000 bits of debris larger than 10 centimeters. (If it sounds like it's getting a bit cluttered up there in space, it kind of is.)
Think you know a lot about Earth and our moon? Test your knowledge about our planet, and see how much you know about the basic elements and objects found in our galaxy and in our solar system.