probes according researchers implies density gradient large scale feature vlism local interstellar medium general direction heliospheric nose ref name sa ref ref name ajl ref interaction interplanetary medium ibex 's interstellar matter observations interstellar medium begins interplanetary medium solar system ends solar wind slows subsonic velocities termination shock astronomical units sun region beyond termination shock called heliosheath interstellar matter interacts solar wind ''voyager '' farthest human made object earth crossed
Natural science Space science Interstellar medium