Voyager Spacecraft Detect An Increase In the Density of Space Outside the Solar System

As Voyager 2 moves farther and farther from the Sun, the density of space is increasing. “It’s not the first time this density increase has been detected,” notes SciencAlert. “Voyager 1, which entered interstellar space in 2012, detected a similar density gradient at a separate location.” From the report: Voyager 2’s new data show that not only was Voyager 1’s detection legit, but that the increase in density may be a large-scale feature of the very local interstellar medium (VLIM). The Solar System’s edge can be defined by a few different boundaries, but the one crossed by the Voyager probes is known as the heliopause, and it’s defined by the solar wind.
[…] One theory is that the interstellar magnetic field lines become stronger as they drape over the heliopause. This could generate an electromagnetic ion cyclotron instability that depletes the plasma from the draping region. Voyager 2 did detect a stronger magnetic field than expected when it crossed the heliopause. Another theory is that material blown by the interstellar wind should slow as it reaches the heliopause, causing a sort of traffic jam. This has possibly been detected by outer Solar System probe New Horizons, which in 2018 picked up the faint ultraviolet glow resulting from a buildup of neutral hydrogen at the heliopause. It’s also possible that both explanations play a role. Future measurements taken by both Voyager probes as they continue their journey out into interstellar space could help figure it out. But that might be a long bet to take. The findings have been published in The Astrophysical Journal Letters.