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Voyager-2 has found more particles in interstellar space than researchers expected, writes the science portal Science Alert.
After a 41-year journey, in November 2018, NASA’s spacecraft, known as Voyager-2, left the Solar System and entered interstellar space. However, his mission is not over, he constantly sends information about what is in this completely unknown region.
The first results are definitely surprising:
As the device moves away from the Sun and its influence, it encounters an increasingly dense plasma.
In another part of interstellar space, Voyager-1, which left the Solar System in 2012, felt similar.
All of this suggests that increasing plasma density may be a general trend in nearby interstellar space.
Heliosphere and heliopause
Interplanetary space, and beyond, a vast expanse of space, is filled with plasma emanating from the Sun. This flow is the solar wind, which is made up of high-energy electrically charged particles. The space that fills the plasma is called the heliosphere, that is, the sphere of the Sun. Outside the heliosphere, we are already talking about interstellar space, and between the two there is a kind of boundary layer, the heliopause.
Beyond the heliopause, the pressure of the solar wind is no longer strong enough to withstand the wind coming from interstellar space.
The Voyagers managed to cross this boundary layer.
Unexpected increase in density
Outer space is generally considered a vacuum, but it contains matter at a very low density. Within the Solar System, the average density of protons and electrons of the solar wind is 3 to 10 particles per cubic centimeter, but this value decreases as it moves away from the Sun.
Previous estimates assumed 0.037 electrons / cm in interstellar space in the Milky Way.3 the density of the plasma, while in the outer heliosphere this value is 0.002 electrons / cm3.
Voyager reported higher plasma densities than expected: in 2013, Voyager-1 0.055 electrons / cm3measured at a distance of 18.3 billion kilometers. Similar results were obtained years later, in January 2019, Voyager-2, which indicated a value of 0.039, at which time the probe was 17.8 billion kilometers from the Sun.
As they moved through interstellar space, both devices sent data with sharp increases in density. Voyager-1, traveling 21.2 billion kilometers, has 0.13 electrons / cm3, the Voyager-2 sensor at 18.5 billion kilometers is 0.12 electrons / cm3He showed.
What could be in the background?
Currently there are two theories, one is that the interstellar magnetic field causes the phenomenon. The theory is consistent with the Voyager-2 observation, which reported a stronger-than-expected magnetic field as it crossed the heliopause.
Another theory blames the interstellar wind, which slows down and becomes “congested” at the heliopause. astronomers are therefore continuing their investigations.
A study presenting the Voyager-2 results was published in the astrophysical journal The Astrophysical Journal Letters.
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