Where is the edge of the solar system?

What is behind Pluto's orbit?

In 1930, when Clyde Tombaugh discovered Pluto, some theorists wondered that there could be planets or other cosmic bodies beyond Pluto's orbit. Nowadays, telescopes such as the PANSTARRS and the upcoming Vera Rubin telescope scan the entire starry sky in hopes of finding something in the Kuiper belt.The Kuiper Belt is beyond the orbit of Neptune. This is the asteroid belt, which contains many small cosmic bodies, among which Pluto is located. The Kuiper belt is often confused with the Oort cloud, but the Oort cloud is more distant and contains more comet-like bodies. It is believed that the Kuiper belt is the remnants left after the formation of the solar system.


What about the Oort cloud? The existence of the Oort cloud, unfortunately, is still only hypothetical. But theorists believe that it is located at a distance of 50 to 100 thousand astronomical units. But this is not yet the edge of the solar system.Heliosphere and Hill's Sphere

To answer the question of where exactly the solar system ends, you need to understand where the solar wind flies and where solar gravity ceases to dominate.


The zone that is constantly influenced by the solar wind is called the Heliosphere. The limit of the heliosphere - the heliopause is located at a distance of about 100 astronomical units from the Sun. At a distance of 60-70 astronomical units from the Sun, the solar wind begins to rapidly decelerate due to its interaction with interstellar gas, and towards the heliopause, the solar plasma flow is completely balanced by the pressure of interstellar gas.However, the sun's gravity dominates at much greater distances. Some scientists believe that Hill's sphere - the sphere dominated by the gravitational influence of the body, for the Sun extends to 125,000 astronomical units. Therefore, it is this distance that can be called a full-fledged edge of the solar system.


Apparatus located at the edge of the heliosphere

The well-known American spacecraft Voyager 1 and Voyager 2 left Earth back in 1977 to explore the giant planets. In 2012, Voyager 1 went beyond the heliosphere, and in December 2018 the Voyager 2 probe did the same, but despite this, the devices still send signals to Earth.Voyager 2

In addition to the well-known Voyagers, other devices such as Pioneer 10, Pioneer 11 and New Horizons also operate at the edge of the solar system. These vehicles, too, will eventually leave the heliosphere and enter interstellar space, as the Voyagers did.


An interesting fact is that after several tens of thousands of years, the probes can meet with other stars. For example, the Voyager 1, Voyager 2 and Pioneer 11 probes will meet with the star Proxima Centauri, and Pioneer 10 with the small red dwarf Ross 248.


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