Dwarf planet Quaoar has a weirdly big ring of debris encircling it

Quaoar, a dwarf planet in our photo voltaic system, has a hoop of particles orbiting it that’s far additional out than we thought the legal guidelines of physics enable

By Alex Wilkins

The dwarf planet Quaoar, which sits past Neptune in our photo voltaic system, seems to have a hoop of particles round it that’s a lot additional out than was thought potential.

“We have observed a ring that shouldn’t be there,” says Bruno Morgado on the Federal University of Rio de Janeiro in Brazil.

Until now, each ring or orbiting moon noticed by astronomers has obeyed a restrict put ahead by astronomer Édouard Roche in 1848 that pertains to its distance from a mother or father physique. If an object is beneath the Roche restrict, its mother or father physique’s gravity rips aside the orbiting object into a group of smaller chunks which finally type a hoop, like these seen round Saturn. Outside that restrict, mud and particles ought to coalesce to type bigger objects, equivalent to moons.

Quaoar, which is 1110 kilometres throughout and is barely much less dense than our moon, ought to have solely moons past a distance of two.4 instances its radius of 555 kilometres, however Morgado and his colleagues measured the ring at 7.2 instances Quaoar’s radius. “It’s very, very far outside this limit,” says Morgado.

To spot Quaoar’s wayward ring, the group noticed the dwarf planet in opposition to the backdrop of varied stars between 2018 and 2021, utilizing Earth-based telescopes in addition to the European Space Agency’s CHEOPS exoplanet-hunting house telescope. The researchers used modifications within the stars’ brightness to calculate the ring’s traits.

They discovered that the ring seems to be principally made up of water ice, a bit like Saturn’s F-ring. One uncommon property of the ring is its irregular form – some sections are 5 kilometres vast, whereas others span greater than 100 kilometres. Standing on the floor of Quaoar, it’s best to be capable of see among the ring’s wider sections, says Morgado.

It isn’t clear why Quaoar has a hoop to date exterior its Roche restrict, however the researchers suppose that the low temperatures – the dwarf planet is a frosty -220°C – may play a job in stopping the ring’s contents coalescing.

It can also be potential that interactions between the ring’s particles or with Quaoar’s moon, Weywot, could possibly be sustaining the ring. Further observations of Quaoar and extra simulations of the system’s dynamics will probably be wanted earlier than a definitive reply might be discovered, says Morgado.

Whatever the reply is, we’d want to switch the Roche restrict, which may have implications for different calculations in astrophysics.

“This concept has been used to analyse, for instance, the formation of our moon and the formation of other satellites in the solar system,” says Morgado. “So, if we have seen something that challenges this limit, we need to rethink and better understand why this ring is where it is.”

Carl Murray at Queen Mary University of London is hopeful that this gained’t change issues an excessive amount of, as a result of the Roche restrict is barely a tough information, however understanding Quaoar’s uncommon ring will assist refine it, he says.

“The Roche limit has its uses, but in reality there’s no exact radius,” says Murray. “It’ll depend on the physical properties of the material that’s orbiting and, as they’ve shown here, there are other characteristics that need to be taken account of as well.”

Sign as much as our free Launchpad publication for a voyage throughout the galaxy and past, each Friday