"Voyagers" helped to clarify the structure of the solar system's heliosphere

Alpha Centauri a and b, the nearest neighboring stars

The boundaries of the solar system are far beyond the last orbit of a planet or planetoid. We can say that the borders of our system are the walls of the heliosphere. The heliosphere itself is a region of near-solar space where the plasma of the solar wind moves relative to the Sun at supersonic speeds. Wikipedia tells us that outside the heliosphere is limited by the so-called collisionless shock wave. It occurs in the solar wind due to its interaction with the interstellar plasma and the interstellar magnetic field.

Man has not yet reached the heliopause — the outer limits of the solar heliosphere — if we mean a manned expedition. On the other hand, two automatic probes that were launched many years ago reached these limits: these are Voyager-1 and Voyager-2. As for the first probe, in 2012, it entered the space where there is no pressure of the solar wind. Then the devices of the device five times recorded jumps in the number of protons and nuclei of helium with an energy of 1.9-2.7 MeV in the surrounding space, with the density of particles with other charges unchanged. According to experts, this indicates a fivefold intersection of the heliopause.

On March 20, the honorary professor of astronomy from the University of New Mexico, Bill Webber, officially announced that Voyager-1 still went beyond the solar system, and it happened on August 25, 2012 at a distance of 121.7 AU. from the sun. Since then, the radiation intensity of 1.9-2.7 MeV has decreased by 300-500 times.
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Now it crosses the Voyager-2 heliopause. He, too, will soon leave the solar system, but the instruments of the device fix a slightly different picture of what is happening when leaving for interstellar space. This was stated by Ed Stone, ex-director of NASA's Jet Propulsion Laboratory. He made his statement at the Conference of the Geophysical Union, which was held last week. So, Voyager 1, as scientists believe, recorded the so-called galactic cosmic rays. But "Voyager 2", crossing the border of the solar system, did not find any rays. In this case, the intensity of the particles remained all the time at the same level.



Perhaps, Stone says, the difference is due to the fact that we are now in the active phase of the solar cycle. The solar wind for this reason is quite powerful, and the number of cosmic rays crossing the boundary of the solar system is not too large. A completely different situation was observed when the Voyager-1 crossed the border. Then the activity of the Sun was lower than now, and a larger number of galactic rays broke through the "boundary". “With this information, we obtained more data on how powerful the barriers of our bubble can be,” says Stone.

The data obtained by the Voyager-2 instruments also indicate that inside the solar power system the solar wind acquires a swirling shape and deviates from the general flow, forming a rather long tail that someone may recall the comet's tail. Previously it was believed that this is exactly what the situation on the border of the solar system should be. But Voyager 1 did not encounter anything like this. He recorded a decrease in wind speed while maintaining the direction of its movement. But Voyager 2 was able to notice something completely different.

Now the probe "Voyager-1", which is located at a distance of about 137 astronomical units from the Sun, is moving towards the constellation Ophiuchus. This constellation is located to the north of the solar equator. As for the "Voyager 2", then this device is from us at a distance of about 113 astronomical units. He moves in the other direction - towards the constellation Peacock, located in the south. Probably, in the interstellar space, the apparatus will be in the coming years.

According to Stone, the information transmitted by Voyagers helps to understand how stars interact with the circumstellar space. Previously, experts could only make predictions and make assumptions. Now in the hands of specialists were reliable data obtained by two probes "Voyager".

As mentioned above, these devices have worked for many years, and for about twenty years they will continue to function. True, the systems have very little plutonium-238, the decay energy of which is used by probes. Within a couple of decades, the probes will be silent forever. Now scientists are gradually disconnecting some modules of the devices, since the generated RTG energy is no longer enough for the operation of all the probe modules.

So far, the Voyagers movement has continued, data is regularly being sent to Earth, and scientists are carefully analyzing them. By the way, it was the analysis of the signals of the device that made it possible to study in more detail Uranus and the satellites of this giant planet. The fact is that “Voyager-2” flew past this planet 30 years ago and was able to gather information about this planet and its satellites. Thanks to these very data, astronomers from the University of Idaho managed to find out that the planet may still have two small satellites that may well be located in the two rings of Uranus, which complicates the identification of these planetoids.