Even though the Bubble Nebula was first discovered in 1787, our most complete view of it didn't come until April 2016, when a mosaic of four images was released from the Hubble Space Telescope's Wide Field Camera 3. This mosaic showed the nebula in its entirety, including the almost perfectly round shell that gives it its name. That shell is caused by a star 20 times the mass of our sun emitting a powerful flow of gas, or solar wind, that pushes its surrounding material outward into a bubble-like shape. Confined by a molecular cloud that's constantly resisting this outward push, the sphere is nonetheless growing, its ten-light-year diameter expanding outward at more than 100,000 kph (62,000 mph). The strangest thing about the nebula, however, is where this star is located. For a shape this round, you might expect the star to sit in the center, but it doesn't. It sits off to one side. Astronomers aren't quite sure why this is the case, adding extra mystery to an already fascinating astronomical body. We've collected some awesome videos on this topic. Watch them now to learn more.