At the beginning of the year, the New Horizons interplanetary station photographed an asteroid in the Kuiper belt, an area where small celestial bodies are clustered very far from Earth, beyond Pluto's orbit. It is believed that the Kuiper belt formed from what was left after the formation of the planets of the solar system. According to recent calculations, there was another ice giant like Neptune in the solar system, and it is possible that it still revolves around the sun.
Where is the proto-substance hiding
In the middle of the 20th century, astronomers put forward a hypothesis: somewhere beyond the orbit of Neptune, there is a reservoir of special cosmic bodies - planetary earths. These are clumps of dust, stones, ice from a protoplanetary cloud. They are considered the embryos of the planets.
In 1992, the hypothesis was confirmed: they discovered dwarf bodies beyond the orbit of Neptune, at a distance of 30-55 astronomical units. In honor of the Dutch-American astronomer Gerard Kuiper, this area was named the Kuiper Belt.
Inhabitants of the Kuiper belt
Astronomers now know about two thousand objects in this region of the solar system. It is assumed that there are about one hundred thousand bodies with a radius of more than one hundred kilometers. Some move in almost circular orbits, others in highly elongated, with a huge semiaxis of hundreds of astronomical units. Probably, something strongly distorted their trajectories, so scientists talk about a “hot” population as opposed to a “cold” one, with undisturbed orbits.
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In the "cold" population, most of the objects are twinned - for example, the asteroid Ultima Tule, with which the New Horizons spacecraft approached in January of this year. The celestial body looks one, but in fact they are two small objects of the same color and, probably, composition.
The most detailed photograph of Ultima Thule, taken from a distance of 6.6 thousand kilometers.
There is a category of bodies whose orbits are in resonance with the orbit of Neptune. That is, the ratio of the periods of revolution around the Sun is a multiple of whole numbers, say, 2: 3 or 3: 1. Such objects from time to time come closer and influence each other through the forces of gravity, like the Earth and the Moon.
A special type is Trojan asteroids. These are small rocky-ice bodies in orbit of the planet, but moving in resonance with it: in front or behind at Lagrange points, where the gravitational influences of the Sun and the planet are balanced. Jupiter has such. As it turned out, Neptune also possesses Trojans. It is believed that these asteroids were captured and brought into the Kuiper belt from outside.
The so-called scattered disk is very interesting. These are the remnants of planet earths that have traveled since the beginning of the formation of the solar system. They never found a stationary orbit, although some temporarily fell into resonance with Neptune and lingered in the Kuiper belt.
Among them, a fossil scattered disk is distinguished - bodies in orbit with a semi-major axis of about 500 astronomical units (for example, the dwarf planet Sedna). Due to the very elongated orbits, but at perihelions of only 35-40 astronomical units, these objects are not affected by Neptune. They are very difficult to observe, and scientists believe that there may be many "fossils", they account for the bulk of the Kuiper belt.
The Kuiper Belt is located beyond the orbit of Neptune. He owns about two thousand bodies, including 31 dwarf planets. Illustration by RIA Novosti.
How much substance is there
As calculated at the Institute of Applied Astronomy of the Russian Academy of Sciences (St. Petersburg), the mass of the Kuiper belt is two orders of magnitude less than two Earth masses. “The total mass of all objects, and there are large bodies like Pluto, is about fifty times the total mass of the asteroid belt. This gives rise to speculations about the origin of the solar system. Some believe that there was initially more matter beyond the orbit of Neptune. According to other ideas, the giant planets traveled through the solar system, approached the Sun, then moved farther away, "- says RIA Novosti co-author Elena Pitieva, head of the laboratory of ephemeris astronomy. The mass of the Kuiper belt must be taken into account when calculating the motion of planets and spacecraft. “The influence of the Kuiper belt is pretty big. Because of it, the orbits of nearby planets are displaced by several kilometers in ten years ",- clarifies Pityeva. In Russia, there is no way to observe Kuiper belt objects. The only telescope with a six-meter mirror capable of this, BTA in the Caucasus, works mainly for astrophysics. Astrometry, that is, determining the position of objects in the sky, was done at the Pulkovo Observatory. But her fate is now in question.
Jumping giant
In a recent review, scientists from France and the United States describe the history of the Kuiper belt using the Nice model developed in 2005. According to her, the solar system was more compact, the planets revolved around the star in circular orbits and were located closer to each other than now. Then, after removing the gas from the system, the entire "structure" began to move, the planets changed orbits, scattering and dispersing protoplanetary matter. All that remained behind Neptune, as well as captured objects such as Trojan asteroids and unstable satellites, formed the Kuiper Belt. Probably, from there, some of the comets were thrown out by the giant planets even further - into the Oort cloud. This is the name of a hypothetical zone on the very outskirts of the solar system, at a distance of ten thousand astronomical units. According to the review authors,Nice's model is consistent with many observed facts and allows a number of assumptions to be made that have already been experimentally confirmed or verified. But there are also inconsistencies. Scientists have developed their own version of the Nice model - NM12 (the abbreviation of the names of the authors and the year). It is most effective if it is assumed that there were five or more giant planets in the solar system, and then there are four left. The scenario is something like this. Four billion years ago, the solar system began to form from a gas and dust cloud. After six million years, the planets became cramped and they began to change orbits. Saturn and Jupiter jumped far, pushing the unnamed ice giant out of our planetary system. Uranus and Neptune moved away from the Sun and after a hundred million years reached their present location. It is not excludedthat the fifth ice giant is still in the solar system - in orbit much further than the Neptunian. This idea was expressed by American astronomers Konstantin Batygin and Michael Brown in 2016, after analyzing the anomalous orbits of scattered objects in the Kuiper belt, including Sedna, which cannot be explained by the influence of known planets. These orbits are very elongated and the perihelions are grouped into one area. As if something very massive influenced them. So the hypothesis about the ninth planet arose - still not confirmed and not refuted. Perhaps it will be possible to verify it in the coming years with the help of observations with telescopes or in the planned space missions to Uranus and Neptune.analyzing the anomalous orbits of scattered objects in the Kuiper belt, including Sedna, which cannot be explained by the influence of known planets. These orbits are very elongated and the perihelions are grouped into one area. As if something very massive influenced them. So the hypothesis about the ninth planet arose - still not confirmed and not refuted. Perhaps it will be possible to verify it in the coming years with the help of observations with telescopes or in the planned space missions to Uranus and Neptune.analyzing the anomalous orbits of scattered objects in the Kuiper belt, including Sedna, which cannot be explained by the influence of known planets. These orbits are very elongated and the perihelions are grouped into one area. As if something very massive influenced them. So the hypothesis about the ninth planet arose - still not confirmed and not refuted. Perhaps it will be possible to verify it in the coming years with the help of observations with telescopes or in the planned space missions to Uranus and Neptune.it will be possible to verify it in the coming years with the help of observations with telescopes or in planned space missions to Uranus and Neptune.it will be possible to verify it in the coming years with the help of observations with telescopes or in planned space missions to Uranus and Neptune.
The orbit of a hypothetical ninth planet, calculated from anomalous Kuiper belt objects.
Tatiana Pichugina
