Rings in the solar system aren’t exactly uncommon. Half of the planets have them and others may be in the past. Some asteroids, such as the dwarf planet Haumea, have rings. Even the sun has some kind of ring. Now astronomers have discovered an entirely new ring system. That alone scratched their heads as it was unlike anything in the solar system.

Quaoar, a small dwarf planet suspended in the Kuiper belt beyond Pluto, is also surrounded by a dense ring – a ring orbiting at such a great distance that it still needs to stick together like the moon. The discovery means scientists may need to revise our understanding of how moons and rings form and are affected by gravitational interaction with their larger companions.

Just 1,110 kilometers (690 miles) in diameter, Quaoar was discovered in 2002 and has turned out to be a pretty interesting little ball of rock over the years. There are signs of glacial volcanism, and there is even a cute little bear named Weivot with a diameter of only 170 kilometers. But in 2021, astronomers noticed something else. They watched as Quaoar, a dark shadow in the far reaches of the solar system, took position to obscure a distant star; this is a type of observation called occultation. Observations using a ground-based telescope in Australia have shown that the dwarf planet may contain a ring.

A team of astronomers led by astronomer Bruno Morgado of the Federal University of Rio de Janeiro in Brazil set out to see if they could find any more evidence. But point a telescope at a small dwarf planet in the deep darkness of the Kuiper Belt and you can’t expect to see any detail, let alone the rings.

Instead, researchers had to rely on data collected by several ground-based telescopes between 2019 and 2020, looking for more eclipses and eclipse observations (Keops) that he and his team collected in 2021 with the European Space Agency’s (ESA) Characterization Satellite ExOPlanet. . Cheops in space was needed to show that terrestrial clues to the ring are not the result of atmospheric perturbations.

As a result, the combined data provided more than a clue.

“Taking it all together, we saw decreases in brightness that were not caused by Quaoar, but suggesting the presence of material in a circular orbit around it,” says Morgado. “As soon as we saw it, we said, ‘OK, we see a ring around Kvaoar.

These data allowed the researchers to characterize the ring, and things got really weird here. The ring orbits the dwarf planet at a distance of 4,100 kilometers, or about 7.4 Quaoar radii, from the center of Quaoar. (For the record, Weivot is much further away, 24 radius away). However, the border of Roche Quaoar is only 1,780 kilometers from the center of Quaoar.

The rings of other bodies in the solar system are within Roche limits. The Roche limit is the critical distance from a body at which tidal forces, i.e. gravity, will pull it into a mixed pile of rubble as the gravitational force of the larger body exceeds the gravitational force needed to hold the smaller body. Source