More than 40 years after the launch of NASA’s Voyager 2 probe, scientists have interpreted the first data dispatch since it arrived in interstellar space, The Guardian reports. Five papers published this week in Nature Astronomy reveal new information about the boundary at the edge of the heliosphere, the sun’s bubble of charged particles that extends in all directions around the star. Instead of fading out gradually, the boundary was quite distinct, the researchers say. The probe—and its twin, Voyager 1—also give some indication of the shape of the bubble, which likely looks something like a blunt bullet. Scientists expect the probes to run out of power in the mid-2020s—and once they die, researchers say, they will continue on their trajectories for billions of years to come.