A group of researchers from Princeton University, the University of Texas at San Antonio, the University of Waikato, Los Alamos National Laboratory, and the Southwest Research Institute discovered rippled structures in space near the solar system’s equator. The group describes analysing data from Voyager 1 and 2 as well as NASA’s Interstellar Boundary Explorer (IBEX), which circles the Earth, in their paper published in the journal Nature Astronomy to learn more about the nature of space at the solar system’s boundary.
Previous research has shown that at the solar system’s outskirts, the solar wind slows to the speed of sound—this is known as the termination shock. Prior research has also revealed the existence of a point at which the solar wind becomes incapable of pushing back against the pressure exerted by interstellar space—this point is known as heliopause. Both Voyager space probes have crossed this boundary and entered interstellar space. They also sent back sensor data as they did so. In addition, NASA launched IBEX into orbit in 2009 with the goal of studying the characteristics of the solar system’s boundaries.
The researchers discovered a sudden change in pressure exerted by the solar wind in 2014 by analysing data from all three sources, and they used the event’s relatively short time scale to study the shape of the heliopause and termination shock. They were able to quantify the energised neutral atoms produced when the solar wind collided with the interstellar wind.
The researchers were able to use the data as a form of cosmic echolocation because some of the atoms managed to escape into interstellar space while others were bounced back into the solar system. When the researchers modelled the boundary areas, they discovered massive ripples.
They also discovered significant shifts in the distance to the heliopause, indicating that its shape was not uniform and was constantly changing for unknown reasons. The researchers hope to learn more about the solar system’s boundary by analysing data returned to Earth by a new probe set to launch in 2025, which will be capable of sending back more precise measurements of neutral atom emissions.