On the outskirts of our star system is the Kuiper belt. It passes beyond the orbit of Neptune, so it was extremely difficult to see anything in this space before. However, since powerful telescopes have appeared at the disposal of man, several discoveries have been made. So, for example, it became known that the trans-Neptunian object is the main unit that makes up the Kuiper belt, the Oort cloud and the scattered disk. It is worth taking a closer look at the bodies rotating in the "backyard" of the solar system.
TNO
Transneptunian object - a cosmic body revolving around the star in orbit. The most famous of these objects is Pluto, which until 2006 was considered a planet. However, today Pluto is the second largest trans-Neptunian object. The average distance to the star of these bodies is greater than that of the outermost planet in our star system– Neptune.
Currently, more than one and a half thousand such objects have been discovered. However, scientists tend to believe that in fact there are much more of them.
The largest trans-Neptunian object is Eris. It was opened in 2005. The body that has no name and appears in the lists under the number V774104 is the most distant from our luminary. It is 103 AU from the Sun.
All TNOs are divided into four groups.
Separate HNOs
In the solar system there is a subclass of this type of bodies: a separate trans-Neptunian object. It is named so for the reason that the perihelion points of such bodies are located at a considerable distance from Neptune, which means that they are not affected by its gravity. This position makes these planets practically independent not only from Neptune, but also from the entire solar system as a whole.
Formally, these objects are the bodies of an extended scattered disk. Currently, nine such bodies are reported, but this list is likely to be significantly increased in the near future.
One of the representatives of this group of TNOs is Varuna. Opened in November 2000.
Classic Kuiper Belt Objects
The name of this group of bodies comes from the numbering of the first of them - QB1. That is why the trans-Neptunian object, which is located in the Kuiper belt, is called kubivano (kyu-be-one). The orbit of these bodies lies outside the orbit of Neptune, while they themselves do not havepronounced orbital resonance with the planet.
The orbits of most of the cubewanos are almost circular, close to the plane of the ecliptic. Many of these bodies are inclined at a very small angle, while others have significant angles of inclination and more elongated orbits.
The main features of the bodies included in this group are the following:
- Their orbit has never crossed that of Neptune.
- Objects are not resonant.
- Their eccentricity is less than 0.2.
- Their Tisserand exceeds 3.
The classic representative of this group is Quaoar, one of the largest bodies in the Kuiper belt. Opened in 2002.
Resonant TNOs
Resonant are those trans-Neptunian objects whose orbit is in orbital resonance with Neptune.
A close study of such objects makes it possible to speak about the narrowness of the boundaries of resonant objects. In order to stay within these limits, the body needs energy in a certain amount, no more, but no less. Getting the orbit out of resonance is very simple: a slight deviation of the semi-major axis from the established boundaries is enough.
As new objects were discovered, more than a tenth of them were found to be in 2:3 resonance with Neptune. It is believed that this ratio is not accidental. Most likely, these objects were collected by Neptune during its migration to more distant orbits.
Before the first trans-Neptunian object was discovered, experts thought thatthe action of the giant planets on the massive disk will lead to a decrease in the semiaxis of Jupiter and an increase in the semiaxes of Uranus, Neptune and Saturn.
One of the representatives of this group is Orc, a trans-Neptunian object located in the Kuiper belt.
Scattered disk objects
These are bodies located in the most remote region of our star system. The density of objects in this area is very low. All bodies of the scattered disk are made of ice.
The origin of this area is not really clear. Most scientists tend to believe that it was formed at a time when the gravitational influence of the planets had insufficient influence on the Kuiper belt, as a result of which its objects were scattered over a much larger area than in our time. The scattered disk, in comparison with the Kuiper belt, is a fickle medium. The bodies in it travel not only in the "horizontal" direction, but also in the "vertical" one, and almost at the same distances. Computer modeling has shown that some of the objects may have wandering orbits, while others are unstable. This suggests that the bodies could be ejected into the Oort cloud or much further.
New Discovery
In July 2016, another trans-Neptunian object was discovered. Its dimensions are very small (diameter - about 200 km), it is 160 thousand times dimmer than Neptune. Its name means "rebellious" in Chinese. The object got its name because it rotates in the direction opposite to the movement of the Sun.system, since this can only be explained by the fact that some sufficiently powerful body acted on it, radically changing its orbit.
This nature of the new object made scientists confused, because at the moment it is not clear which planet and how could make the "rebel" move in such an orbit. Astronomers are again thinking about the existence of a planet unknown to us, which can have such strong effects on other bodies.
