Interstellar space turned out to be dense enough

Huge spaces in the universestretching between stellar systems is commonly called interstellar void. It is assumed that the density of matter in this space is quite low. Determining the boundaries of the solar system, after which the interstellar void begins, is the subject of many years of scientific debate. It was proposed to use the concepts of the heliosphere and heliopause as one of the parameters. The heliopause is the boundary of space in which the force of the solar wind is equalized with the external pressure of the interstellar medium. The heliosphere is the space within the sphere limited by the heliopause. It is assumed that the interstellar void is located outside the heliosphere.

Astronomers, using theoretical calculations,determined the density of the void inside the Milky Way at the level of 0.037 particles per cubic meter. cm. In this case, the density of space outside the heliopause was defined as 0.002 electrons per cubic meter. centimeter. However, when the spacecraft Voyager 1 and Voyager 2 reached the boundaries of the heliopause, it turned out that the bottom line was fundamentally at odds with the calculations on paper.
The first, back in 2013, overcame the helopauseVoyager 1, having moved 18.1 billion km from Earth on October 23. Measurements of the density of the space located behind the heliopause gave the result of 0.055 electrons per cubic meter. cm.

Six years later, Voyager 2 reachedthe boundaries of the heliosphere and on January 30, 2019, carried out similar density measurements at a distance of 17.9 billion km from the Earth. The result was 0.039 electrons per cubic meter. see. However, the most surprising thing is that with the distance from the Earth, the density of matter surrounding Voyagers began to increase. So "Voyager 1" at a distance of 21.2 billion km from the Earth received the result of 0.13 electrons per cubic meter. cm, and "Voyager-2" "flying away" from the Earth by 18.5 billion km determined the density of space at 0.12 electrons per cubic meter. cm.

According to the version, this inconsistency with the theoryscientists are the two most logical options for justification. According to the first version, the magnetic field in the heliopause zone is unstable and Voyager 2 simply recorded the moment of the field “excitation”. The second theory states that at the point where the pressure of the solar wind and interstellar space is equal, elementary particles begin to accumulate, increasing the density of space.

Source: iopscience