A graphic representation of the heliosphere, a vast bubble-like structure defining the extent of the solar wind and the Sun’s electromagnetic influence on the local environment. The heliosphere is distorted by the solar system’s motion through the interstellar medium. A proposed Interstellar Probe would venture much farther into interstellar space than either of NASA’s Voyager spacecraft. Image: NASA/JPL-Caltech A proposed NASA mission to send a probe outside the solar system to study the Sun’s interstellar environment and the heliosphere, the vast bubble-like region marking the extent of the solar wind, is gaining momentum at the Johns Hopkins Applied Physics Laboratory.