The heliosphere is the region of space dominated by the Sun that cocoons Earth and the other planets. Inflated by the million-mile-per-hour solar wind, the bubble-shaped heliosphere pushes its way through the galaxy. For a quarter century, researchers believed a bow "shock" formed ahead of the heliosphere as it moved through interstellar space – similar to the sonic boom made by a jet breaking the sound barrier. New data from NASA's Interstellar Boundary Explorer (IBEX) shows that the heliosphere moves through space too slowly to form a bow shock. Credit: Courtesy Southwest Research Institute