The Universe is vast and always changing. It includes planets, stars, galaxies, and all of space, matter, and energy. Looking at the night sky, you can sense how small Earth is in the vastness of space.?A million Earths could fit inside the Sun.?The Sun is the only star in our Solar System, but is one of over 100 billion stars in a spiral galaxy we call the Milky Way. Astronomers think that most of the stars in our galaxy may also have planets orbiting around them. See if you can find where our Solar System is located in our galaxy.