(ORDO NEWS) — The space bubble surrounding the solar system can be wrinkled, at least sometimes.
Data from a spacecraft orbiting the Earth has revealed ripples in the final impact and heliopause: shifting regions of space that mark one boundary between the space inside the solar system and that outside – interstellar space.
The results show that it is possible to get a detailed picture of the boundary of the solar system and how it changes over time.
This information will help scientists better understand the region of space known as the heliosphere, which recedes from the Sun and shields the Solar System’s planets from cosmic radiation.
There is such data. various ways in which the sun influences the space around it. One of them is the solar wind, a constant supersonic flow of ionized plasma. It passes planets and the Kuiper belt, eventually disappearing into the vast void between the stars.
The point at which this flux falls below the speed at which sound waves can propagate through the diffuse interstellar medium. is called the final shock wave, and the point at which it is no longer strong enough to counteract the very weak pressure of interstellar space is called the heliopause.
Both Voyager probes crossed the heliopause and, in fact, now travel through interstellar space, providing us with the first in situ measurements of this moving boundary.
But there is another tool in Earth orbit that has been helping scientists map the heliopause since its launch in 2009: NASA’s Interstellar Frontier Explorer (IBEX).
IBEX measures excited neutral atoms that form when the Sun’s solar wind collides with interstellar wind at the edge of the solar system. Some of these atoms are catapulted further into space, while others are thrown back to Earth.
Given the strength of the solar wind that generated them, the charged neutral particles that come back our way can be used to map the shape of the boundary, a bit like cosmic echolocation.
Previous maps of the structure of the heliosphere were based on long-term measurements of the evolution of the solar wind pressure and ejections of energetic neutral atoms, which resulted in a smoothing of the boundary both in space and in time.
But in 2014, over a period of about six months, the dynamic pressure of the solar wind increased by about 50 percent.
A team led by astrophysicist Eric Zirnstein at Princeton University used this shorter scale. event to get a more detailed picture of the shape of the final impact and the heliopause – and found huge ripples on the scale of tens of astronomical units (one astronomical unit is the average distance between the Earth and the Sun).
They also ran simulations and simulations to determine how this high pressure wind interacts with the solar system boundary.
They found that the pressure front reached its final shock in 2015, sending a pressure wave through the region between the final shock and the heliopause, known as the inner heliosheath.
At the heliopause, the reflected wave travels backwards, colliding with the still incoming flow of charged plasma behind the pressure front, creating a storm of energetic neutral atoms that fills the inner heliosheath by the time the reflected wave reaches the reverse shock.
The group’s measurements also show a fairly significant 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 in the direction of Voyager 1 is about 131 astronomical units; at the time, the probe was 136 astronomical units from the Sun, still in interstellar space but with a bloated heliosphere behind it.
The team’s measurement of the heliopause in the direction of Voyager 2 in 2015 is a little trickier: 103 astronomical units with an error of 8 astronomical units on each side.
At the time, Voyager 2 was 109 astronomical units from the Sun, which is still within the margin of error. It did not cross the heliopause until 2018 at a distance of 119 astronomical units.
Both measurements suggest that the shape of the heliopause is changing, and this is important. It’s not entirely clear why.
However, a new probe will be sent into space in 2025 to measure the emission of energetic neutral atoms with higher accuracy and over a wider range of energies.
This, the team says, should help answer some puzzling questions about the strange, invisible, “shrunken” bubble that protects our small planetary system from the oddities of space.
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