Strange waves have been spotted at the edge of the solar system

The bubble of space surrounding the solar system could be crumpled, at least at times.

Data from a spacecraft orbiting Earth have revealed wave structures in the final shock and heliopause: shifting regions of space that mark one of the boundaries between space inside the Solar System and that outside the Solar System — interstellar space.

The results show that it is possible to obtain a detailed picture of the solar system boundaries and their changes over time.

This information will help scientists better understand a region of space known as the heliosphere, which emanates from the Sun and protects the planets in our solar system from cosmic rays.

There are a variety of ways the sun affects the space around it. One of them is the solar wind, a constant supersonic flow of ionized plasma. It blows past the planets and the Kuiper belt, and eventually dissipates in the great void between the stars.

The point at which this flow falls below the speed at which sound waves can travel through the diffuse interstellar medium is called termination shock, and the point at which it is no longer strong enough to withstand the very low pressure of interstellar space Pushing back is the heliopause.

Both Voyager probes have crossed the heliopause and are now effectively cruising through interstellar space, giving us the first in situ measurements of this shifting boundary. But there’s another tool in Earth orbit that’s been helping scientists map the heliopause since it began operations in 2009: NASA’s Interstellar Boundary Explorer (IBEX).

IBEX measures energized neutral atoms produced when the Sun’s solar wind collides with the interstellar wind at the solar system boundary. Some of these atoms are catapulted further out into space, while others are catapulted back to Earth. Considering the strength of the solar wind that produced them, energized neutral particles returning on our path can be used to map the shape of the boundary, similar to cosmic echolocation.

Previous maps of the structure of the heliosphere relied on long-scale measurements of the evolution of solar wind pressure and emission of energetically neutral atoms, resulting in a smoothing of the boundary in space and time. But in 2014, the stagnation pressure of the solar wind increased by about 50 percent over a period of about six months.

A team of scientists led by Princeton University astrophysicist Eric Zirnstein has used this shorter event to obtain a more detailed snapshot of the shape of the termination shock and heliopause – and in the process detected giant waves on the scale of tens of astronomical units (1 astronomical unit is the average distance between the earth and the sun).

They also performed modeling and simulations to determine how this high-pressure wind interacts with the solar system boundary. They found that the 2015 pressure front reached termination shock and sent a pressure wave through the region between termination shock and the heliopause known as the inner helioseath.

At the heliopause, a reflected wave travels back, colliding with the still-inflowing charged plasma behind the pressure front and creating a storm of energetic neutral atoms that fills the inner heliseaath when the reflected wave arrives at the termination shock again.

The team’s measurements also show a fairly clear shift in the distance to the heliopause. Voyager 1 crossed the heliopause in 2012 at a distance of 122 astronomical units. In 2016, the team measured that the distance to the heliopause towards Voyager 1 was about 131 astronomical units; at the time, the probe was 136 astronomical units from the Sun, still in interstellar space but with a ballooning heliosphere beyond.

The team’s measurement to the heliopause towards Voyager 2 in 2015 is a bit trickier: 103 astronomical units with an error margin of 8 astronomical units on either side. At this point, Voyager 2 was 109 astronomical units from the Sun, which is still within error. Only in 2018 did he cross the heliopause at a distance of 119 astronomical units.

Both measurements indicate that the shape of the heliopause is changing, and not insignificantly so. It’s not entirely clear why.

In 2025, however, a new probe will be sent into space to measure emission from energetically neutral atoms with greater precision and over a wider energy range. That, the team says, should help answer some of the perplexing questions about the strange, invisible, “wrinkled” bubble that protects our tiny planetary system from the strangeness of space.

The research was published in natural astronomy.