NASA has been studying the solar system and has found that on the boundary of the solar system, pressure runs high. The pressure in the region is the force that plasma, magnetic fields, and particles such as ions, cosmic rays, and electrons exert on each other as they collide. This force was found to be greater than expected by NASA scientists.
The team used observations of galactic cosmic rays, which is a highly energetic particle in the outer region of the solar system that were made by the Voyager spacecraft. Using that data, the scientists calculated the total pressure of particles in the outer region of the solar system, which is called the heliosheath. That region is challenging to study due to the vast distance from Earth.
What made the detailed study possible was the positioning of the Voyager spacecraft and the convenient timing of a solar event. The scientists used measurements from Voyager 1, which was outside the heliosphere and in interstellar space. Measurements from Voyager 2, still inside the heliosheath, were taken as well.
The solar event that contributed to the measurement was called the global merged interaction event that created a giant wave of plasma. The team says that Voyager 2 detected one such wave and noted that the number of galactic waves temporarily decreased. Four months later, Voyager 1, which was just across the solar system’s boundary in interstellar space, saw a similar decrease.
Knowing the distance between the spacecraft allowed the scientists to calculate the pressure of the heliosheath as well as the speed of sound. In the heliosheath, the speed of sound is about 300 kilometers per second, which is a thousand times faster than sound moves through air.