Quaoar is about half the size of Pluto: 1100 versus 2370 kilometers in diameter. That is, it is about the same as Pluto’s satellite Charon. For comparison, the diameter of the moon is 3474 kilometers. Quaoar is located mostly far beyond Pluto, but since Pluto’s orbit is very elongated, it regularly climbs beyond the orbit of Quaoar. Recall that Pluto was demoted from the planets precisely because behind Neptune there was a whole collection of celestial bodies of similar dimensions.
It is interesting that even such a relatively tiny planet also has its own moon: the 160-kilometer Veyvot satellite, it is located more than 14 thousand kilometers from Quaoar. Again, for comparison: from the Earth to the Moon – an average of 384 thousand kilometers.
But not so long ago it turned out that Quaoar not only has its own moon in stock. Some objects were noticed near it, which are usually not visible through a telescope. The fact is that often, for a more detailed consideration, astronomers observe a celestial body during its passage in front of the disk of a star. The most spectacular and accessible is, say, to see how Mercury or Venus follow the disk of the Sun. And when, when observing some distant star, it periodically dims and becomes brighter again, for astronomers this indicates that this star has its own planet. Or even several planets. This is called the transit method of observation. And exactly in this transit method, during the passage right in front of some star, Quaoar was observed. And it turned out that in addition to the satellite – Veyvot – he has two whole rings. Of course, they are not as amazing as those of Saturn, but still there. By the way, not only Saturn has rings in the solar system, but all gas giants in general, and not only them: scientists have seen the same decoration even in another dwarf planet Haumea. This is the one that is not spherical, but in the shape of a bean or a rugby ball.
Dwarf planet Quaoar. Photo © NASA and G. Bacon
Of course, the rings around the planets are beautiful and amazing in themselves, but that’s not the point. The fact is that at Quaoar they are located where, according to all calculations, they cannot be in any way. And why not: in astronomy there is such a term – the Roche limit. This is in honor of the French scientist Edouard Roche, who calculated this limit. This is such a boundary that divides the circumplanetary space into the territory of the rings and the territory of the satellites. That is, the rings should be closer than this Roche limit, and the satellites should be further. Why: because the gravity of the planet, as a body approaches it, at some point begins to crush it into small fragments and thus can scatter it into a whole ring, which will then circle around the planet for a very long time. And beyond the Roche limit, this gravity no longer has such a destructive effect, and there such a placer, on the contrary, can and should, literally in a few decades (maximum over a century), gather into a single whole and form at least some kind of Wavet – in general, a monolithic body. Each planet has its own Roche limit, because each planet has its own individual dimensions and its own individual gravity. Eg, in this scientific work it is said that for the Earth the Roche limit is about 19 thousand kilometers. This means that a natural satellite cannot exist closer than this distance, it must crumble into a ring. And, fortunately, our Moon is very, very far from this dangerous limit – and, thus, the rule is observed, the situation is clear. But if we were in the place of the Moon, that is, at its own distance, instead of it, we would observe some magnificent ring, then astronomers would plunge into deep reflections: as far as they know, this is impossible. At least this ring in fifty years should turn back into the Moon.
So, for Quaoar, this limit of possibilities is at a distance of 1780 kilometers from the center of the planet. That is, rings are supposed to be in this radius, then – sorry, only satellites are accredited. And what about this actually watching: one ring at a distance of 2500 kilometers, the other – and more than four thousand kilometers at all. The question is, how do they manage to break the laws of physics with impunity and penetrate where they are not allowed to enter?
On the one hand, it is still not entirely clear how long Quaoar has been in this form. Maybe in twenty years these rings will dissolve, or rather, on the contrary, they will coalesce into two more Veyvots. But for now, astronomers proceed from the fact that they are not observing a short-term situation, but a certain permanent phenomenon, and some explanation must be sought for it. And the only thing that comes to the minds of scientists today is the influence of Veyvot itself. There is such a phenomenon in space: if the movement of one satellite of the planet in its orbit is somehow “synchronized” with the movement of another, then this enhances their mutual attraction. And how can it be “synchronized”? Let’s say one satellite makes a revolution around the planet in three days, and the other manages to make two whole revolutions in the same time. This is called orbital resonance. In this example, an orbital resonance of 1 to 2 is obtained. And in the same way, you can “synchronize” with the rotation of the planet itself around its own axis. Then it will be a spin-orbital resonance. And this also works in the sense of mutual gravity.
And scientists have calculated that the far ring of Quaoar is in resonance with its small moon 6: 1, that is, while the satellite makes one revolution, the ring makes six. And with the rotation of Quaoar around itself, this ring is “synchronized” 1 to 3: one revolution of the dwarf planet around its axis is equal to three revolutions of the ring. And the nearest ring also falls into a certain rhythm with Quaoar: 5 to 7. Quaoar makes five turns, the ring makes seven in the same time. Therefore, astronomers suspect that perhaps it is this cosmic sense of rhythm that creates such an incredible situation with the rings.
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