An international team of astronomers led by researchers from Brazil’s National Observatory (ON) has discovered an unlikely ring of material orbiting Quaoar, a dwarf planet in the solar system located beyond Neptune and considered a “junior cousin” of Pluto.
The importance of the discovery is due to the fact that until recently only rings had been observed on large planets, such as Jupiter and Saturn, and that the distance between Quaoar and its ring debunks an ancient astronomical theory about the separation between a body and those who orbit it, the National Observatory said in a statement.
The team that discovered the dense ring of material around Quaoar was led by Brazilian astronomer Bruno Morgado, a researcher at the National Observatory and author of the article published in Thursday’s edition of the international scientific journal Nature (09.02.2023).
According to the ON, only from 2013 began to be observed that some small celestial bodies, such as the asteroid Chariklo and the dwarf planet Haumea, had rings, as structures formed by dust and other particles orbiting celestial bodies are known.
Quaoar rings
The discovered ring orbits Quaoar, a 1,000-kilometer-diameter asteroid candidate for a dwarf planet in the solar system. Its distance from the Sun is equivalent to 41 times the distance between the Earth and the Sun.
Morgado, quoted in the ON statement, explained that bodies like Quaoar are practically intact fossils of the formation of the Solar System and therefore cataloguing their physical characteristics is fundamental to understanding how our galaxy was formed.
The ring was discovered thanks to a series of observations made between 2018 and 2021 by a collection of ground-based telescopes and by the space observatory Satellite for the Characterization of Exoplanets (Cheops).
Determine the physical properties of the ring
Its existence was inferred by means of a technique known as occultation, which involves calculating the size and shape of a hidden object from the reduction of a star’s light when it blocks its vision.
“From the analysis of these brightness dips, the researchers were able to determine the physical properties of the ring, such as its width and the amount of material present,” explained the National Observatory.
The “Roche limit” theory
The most unexpected thing about the discovery is that the ring is about 4,100 kilometers from Quaoar, a distance of almost seven and a half times the radius of the dwarf planet, which contradicts the theory known as “Roche’s limit” (1850).
This theory calculates, from the ray of a celestial body, the limit distance in which a material orbits around a ring-shaped planet without clumping together and the necessary for the material to clump together and form a satellite.
“The discovery surprised scientists because, according to the Roche limit, such a ring should not exist,” the ON said.
“Until now observations confirmed Roche’s theory: all the dense rings of the four giant planets, as well as the rings of Chariklo and Haumea, are within the Roche boundary. But the Quaoar ring challenges that limit,” Morgado said.