Trans-Neptunian object: concept, species

On the outskirts of our star system is the Kuiper belt. It passes beyond the boundary of Neptune's orbit, so it was extremely difficult to see anything in this space before. However, since the deployment of powerful telescopes, several discoveries have been made. For example, it became known that the trans-Neptunian object is the basic unit constituting the Kuiper belt, the Oort cloud and the scattered disk. It is worthwhile to consider in more detail the bodies rotating on the "outskirts" of the solar system.

TNO

The trans-Neptunian object is a cosmic body that orbits the light around the luminary. The most famous of these objects is Pluto, considered to be a planet until 2006. However, to date, Pluto is the second largest trans-Neptunian object. The average distance to the body of these bodies is greater than that of the extreme planet in our star system - Neptune.

Currently, more than one and a half thousand such objects are open. However, scientists are inclined to think that there are actually more of them.

The largest trans-Neptunian object is Eris. It was opened in 2005. The most remote from our body is a body that does not have a name and appears in the lists under the number V774104. It is removed from the Sun by 103 astronomical units.

All TNOs are divided into four groups.

Isolated TNOs

In the solar system, there is a subclass of this type of body: an isolated trans-Neptunian object. It is named for the reason that, the perihelion points of such bodies are at a considerable distance from Neptune, and therefore do not experience the influence of its gravity. This situation 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 expanded scattered disk. At present, there are data on nine such bodies, but this list is likely to be significantly increased in the near future.

One of the representatives of this TNO group is Varuna. It was 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 in the Kuiper belt, is called kyubivano (kyu-bi-one). The orbit of these bodies lies outside the orbit of Neptune, while they themselves do not have a pronounced orbital resonance with the planet.

The orbits of most of the kyubivano have an almost circular shape, close to the plane of the ecliptic. A considerable part of these bodies is inclined at a very small angle, the other has significant angles of inclination and more elongated orbits.

The main features of the bodies included in this group are the following:

• Their orbit never intersected with the orbit of Neptune.
• The objects are not resonant.
• Their eccentricity is less than 0.2.
• Their Tisseran criterion exceeds 3.

The classic representative of this group is Kvar, one of the largest bodies in the Kuiper belt. Opened in 2002.

Resonant TNO

Resonance refers to those trans-Neptunian objects whose orbit is in orbital resonance with Neptune.

A close study of such objects makes it possible to speak of the narrowness of the boundaries of resonant objects. In order to remain invariably within these boundaries, the body needs energy in a certain amount, not more, but not less. To ensure that the orbit comes out of resonance is very simple: it is enough to neglect the large semiaxis from the established boundaries.

As new objects were discovered, more than a tenth of them were found to resonate with Neptune 2: 3. It is believed that such a ratio is not accidental. Most likely, these objects were collected by Neptune during migration in more distant orbits.

Before the first trans-Neptunian object was discovered, experts thought that the action of giant planets on a massive disk would lead to a decrease in the semiaxis of Jupiter and an increase in the semi-axes of Uranus, Neptune and Saturn.

One of the representatives of this group is the Orc - a trans-neptune object located in the Kuiper belt.

Objects of a scattered disk

These are the bodies located in the remotest region of our star system. The density of objects in this area is very low. All the 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 environment. The bodies in it travel not only in the "horizontal" direction, but also in the "vertical" direction, and at practically the same distances. Computer modeling has shown that some objects can have wandering orbits, some are unstable. This makes it possible to assume that the bodies can be thrown into the Oort cloud or much further.

New discovery

In July 2016, another trans-Neptunian object was discovered. Its dimensions are very insignificant (diameter - about 200 km), it is 160 thousand times duller than Neptune. Its name in Chinese means "rebellious." Such an object has got its name because it rotates in the direction opposite to the motion of the solar system, since it can only be explained by the fact that any sufficiently powerful body influenced it, radically changing its orbit.

Such a character of the new object made scientists become embarrassed, because at the moment it is not clear which planet and how to make the "rebel" move in such orbit. Astronomers are again thinking about the existence of an unknown planet, which can have such strong effects on other bodies.