Photography - astronomy
Our solar system with the planets
How big is our solar system and where does it end?
Sun
This question is not that easy to answer. If one takes the gravitational sphere of influence of the sun, that is the space where it can bind other celestial bodies to itself, then our solar system ends at the edge of the Oort cloud, which corresponds to a distance of 1.5 light years. The distances in the solar system are often described with astronomical units. An astronomical unit AU is equal to the mean distance between the sun and the earth, which is 150 million kilometers. 63,241 astronomical units-AU, are one light year.
In the past 100 years the picture of the outer solar system has changed fundamentally and several times. Our planets are listed with the ever increasing distance to the sun. After the rock planets Mercury Venus Earth and Mars, the four gas planets Jupiter Saturn Uranus and Neptune follow. The planet Pluto was demoted to a dwarf planet in 2006. Since then it is no longer the ninth and outermost planet in our solar system. The new discoveries beyond the planet Neptune, which is about 30 AU from the Sun, were the reason for this change. Behind the Neptune orbit after about 39 AU the Kuiper belt begins. It moves flat and in the plane of the planets. The planet Pluto is now part of this Kuiper belt. Over 1,600 such bodies have now been found there. It is assumed that comets also originate from the Kuiper Belt. These are the members of the Jupiter family. The discovery of such objects is not easy, the reason for this is their particularly long orbital times around the sun. Even Pluto, which is at the beginning of the Kuiper Belt, needs 248 years for the orbit around the sun. It was discovered in 1930 and it still takes 158 years to get back to the same place where it was discovered. Such objects are best found with very large telescopes. Even the objects that are a few hundred kilometers in size, compared to similarly sized asteroids that are located in the asteroid belt between Mars and Jupiter, reflect sunlight to us that is many thousand times weaker. The amount of reflected sunlight also depends on the size of the body. Even with the largest telescopes, you can only observe the largest objects with a radius of 100 kilometers. According to the calculations, there will be millions of such bodies in the Kuiper Belt. Only with new and more powerful telescopes will one get more information from the Kuiper belt in the future.
But even the end of the Kuiper Belt is by no means the end of our solar system.
Source NASA
The heliosphere, the protective shield for us too
The heliosphere, also known as the solar atmosphere, extends beyond the Kuiper belt. It extends approximately up to 100 AU into interplanetary space and has its origin in the solar corona. This is where the solar wind is generated and our magnetic field is anchored. The heliosphere acts like a protective shield and protects the earth but also the other planets from cosmic rays. However, this shielding is not constant, but is subject to long-term changes. The reason for this is the solar cycle with the associated changes in the magnetic field. Depending on the resistance, the solar wind is influenced by the interstellar medium that moves through our solar system. The interaction of the solar wind and the sun's surroundings have a strong influence on this protective effect. The sun hurls around a million tons of electrons, protons and ions into space every second. The entire solar system orbits the center of our home galaxy at almost 900,000 kilometers per hour in just under 230 million years.
The sun's magnetic field
Source NASA
Our solar system in the Milky Way
Source NASA
Oort cloud the end of the solar system unimaginable dimension
This huge cloud of icy lumps surrounds our solar system, and the sun's gravitational sphere of influence ends at its edge. The Oort cloud extends 300 to 100,000 astronomical units from the sun. All long-period comets whose orbital periods are longer than 200 years come from the Oort cloud. The difference to the flat Kuiper belt which moves in the plane of the planets, this cloud encloses the solar system like an envelope. From the observed frequency of long-period comets, it is estimated that there are billions of such bodies there. That would make it the most important class of these bodies in the solar system. The comets in this cloud are still gravitationally weakly bound to the sun, so that a star passing by by chance can fundamentally change their orbits. As a result, comets can be hurled out into interstellar space or into the inner solar system on elongated ellipses. The distance from the Sun to the nearest star Proxima Centauri is 4.2 light years. This is still 2.7 light years from the edge of the Oort cloud. The Voyager 1 spacecraft was sent on its journey on September 5, 1977 on Cape Canaveral. In September 2017 their distance to the sun was 21 billion kilometers, that is 140 AU. Your current speed is at least 62,140 km / h. That is almost 1,500,000 km that she covers per day and in one year that is 544,346,400 km, which corresponds to about 3.6 AU. The inner edge of the Oort cloud begins at 300 AU. It will take another 45 years to achieve this. Let us assume that Voyager 1 would always cover an average of 3.6 astronomical units per year, then it would theoretically travel 27,778 years from start on Earth to the edge of the Oort cloud. That would be 100,000 AU, or the distance sun-earth 100,000 times. Voyager's batteries will run out in the next few years, but the journey will continue even without radio contact. At least now everyone will be aware that if we should also make it to Mars in the next few years, we will not actually even be in front of our own door. The mean distance between Mars and the Sun is just 1.52 AU. Our home galaxy, the Milky Way, has a diameter of over 100,000 light years. We can no longer grasp these dimensions.
