From the point of entry into the universe Earth space has long since ceased to be exotic, having acquired, among other things, and this attribute developed territory, as a fair amount of debris. And actively explore the more remote areas: spacecraft populated neighborhood of the Lagrange points and the orbit of the Earth, our probes are flying around the five (counting the Earth) of the eight planets in the solar system. It is almost a commonplace, because even from the time when humans from close range saw the most distant planet, Neptune, was more than 20 years.
Then, in the 1970s and 1980s, the path into the outer solar system paved the four apparatus: "Pioneer 10", "Pioneer 11", "Voyager 1" and "Voyager 2". Now they have sent images of the giant planets seem almost history. Meanwhile, the "Voyager", noting in 2012, the 35th anniversary of stay in space, and to this day continue to work and regularly provide information on further outer solar system. "Pioneer 10" and "Pioneer 11" stopped responding to signals from the Earth in 2003 (by the way, on January 23, entirely 10 years ago), and 1995.
Voyage "Voyager" started in 1977. Ironically, the first went into space "Voyager 2", and "Voyager 1" flew the second, but the time to correct this injustice, and now it is "Voyager 1", ahead of fellow, is the most distant man-made object, he retired from the Sun nearly 125 astronomical units (AU), leaving behind not only the big planets in the solar system, but also a significant part of the Kuiper belt.
The current phase of the "Voyager" at NASA is modestly called "The interstellar mission", and in the news about these no-no and slip the assertion that they have left the solar system. But in reality, of course, is not so simple. First, the boundary of the solar system can be defined in different ways, and second, as any definition, this limit will not be striped barrier behind which the spacecraft can immediately assume the interstellar wanderer, thirdly, she moves back and forth in response to the the current level of solar activity.
Given the nature of the equipment working now on "Voyager", the output of the solar system for them is getting into an area not covered by solar wind. This wind – a stream of charged particles, breaking away from the solar surface, blows around the "planet" of the solar system giant bubble – the heliosphere. Heliosphere with the sun moves through the surrounding interstellar cloud, the Local Fluff. Collision zone of solar wind and the interstellar medium (ISM) has a layered structure, the definition of which, by the way, made a significant contribution to our scientists (VB Baranov and others) and the spacecraft.
From the Sun the first line on the way to interstellar space is Heliospheric shock, where the supersonic solar wind begins for "feel" approach interstellar matter and decelerated to subsonic speeds. "Voyager 1" crossed geoliosfernuyu shock in 2003-2004, at a distance of 94 AU from the sun, and "Voyager 2" made it three years later, when away from the Sun was 84 AU It should be clarified that the devices are flying in the same hemisphere: about crowding against the interstellar material in the solar system (the first is in the constellation Ophiuchus, the second – in the constellation of the telescope). However the transition through the shock wave from "Voyager 1" held at a greater distance, which means that the shape of the heliosphere far from spherical.
After that the tedious wait the next frontier – the heliopause at which solar plasma ends and begins interstellar matter, is not in its normal state, and crumpled collision with the heliosphere, but still is not our agent, and someone else who had never been a part of the solar systems. Unfortunately, the "Voyager 1" is not working devices that can determine the parameters of the surrounding matter directly, so approximation heliopause have to look for telltale signs, particularly on the changes in the energy spectrum of cosmic rays.
Earth orbit cosmic rays – accelerated to very high velocities of the atoms of different chemical elements – made up of three components: solar, galactic and anomalous. Solar cosmic rays are born, you guessed it, the Sun and, in fact, are the continuation of the high-energy solar wind. Galactic cosmic rays (GCRs) are born out of the solar system, probably in shock waves in supernovae (although even a little direct evidence of this so far). Anomalous cosmic rays (ACR) were discovered in the early 1970s as a kind of excess of particles with energies of 10 MeV, but the abnormality of their concerns, rather than to energy, and the chemical composition: if the chemical composition of the GCR is not very different from the sun, the ACL in an excess of helium, oxygen, nitrogen and other elements. Before crossing the "Voyager" Heliospheric shock assumed that ACR formed of atoms, which in the ISM are in a neutral state, passing heliopause, ionized, accelerated to high speeds on the heliospheric shock and directly into the solar system already fly with decent speeds.
In accordance with this assumption, it was expected that the shock wave "Voyager" will record growth Flow ACL, but that did not happen: no sudden changes in the intensity of ACR units did not see it. Probably, acceleration is not on the shock wave or not at all sites, yet it is the presence of anomalous cosmic rays in this space is the last (or penultimate) sign the continuing influence of the Sun.
Indications of approaching the heliopause appeared in the data, "Voyager 1" in 2009-2010, when it reported a decline in equipment solar wind velocity to almost zero and at the same time more and more increase in the flux of galactic cosmic rays. In the spring of 2012, "Voyager 1" entered into a region of space where the changes started to take unprecedented. Starting from May 8 for a few days of GCR intensity doubled, two sharp jump occurred on July 28 and August 13. In the latter two cases, while the intensity decreased and ACL.
But these were only the symptoms of the main changes: August 25, 2012 at a distance of 121.7 AU the sun began a sharp drop in the rate ACL, in which she dropped a few weeks in the 300-500 times. Simultaneously at times increased the intensity of GCR. Obviously, at the end of August, "Voyager 1" crossed a gap, for which the particle anomalous cosmic rays can not enter. This month the unit flies about 0.3 AU, but the gap is obviously thinner. It is possible that he is moving at a speed of approximately apparatus and preliminary races the intensity of cosmic rays have been linked to the fact that "Voyager" repeatedly touched the gap before finally cross it.
Although the observed gap and looks like heliopause, JPL NASA experts are in no hurry to say that the unit is permanently in the ISM. This can be judged as "Voyager 1" will bounce away without meeting on the way any new quirks, and when the data will confirm the "Voyager 2". In the meantime, it is encouraging to think that in 2012 we introduced the ability directly measure one of the most important parameters of the interstellar medium of the galaxy – the spectrum of galactic cosmic rays at low energies. In the vicinity of the Earth, this is not possible, because here he is confused with the spectrum of ACL. And to know it would be very interesting, even this far from the physics of high energy person like me, it is the cosmic rays are the main initiating factor in interstellar chemistry. In the calculations, we still use the parameters obtained at the end of the 1960s, only the observations of high-energy GCR (20 MeV). Meanwhile, the chemistry is not less important and may be less energetic particles, which we still do not know anything.