Quaoar, a dwarf planet, is hiding a big surprise – an orbiting ring of debris that shouldn't be there, according to our understanding of planetary physics
, which is 1110 kilometres across and is slightly less dense than our moon, should have only moons beyond a distance of 2.4 times its radius of 555 kilometres, but Morgado and his colleagues measured the ring at 7.2 times Quaoar’s radius. “It’s very, very far outside this limit,” says Morgado.
They found that the ring appears to be mostly made up of water ice, a bit like Saturn’s F-ring. One unusual property of the ring is its irregular shape – some sections are 5 kilometres wide, while others span more than 100 kilometres. Standing on the surface of Quaoar, you should be able to see some of the ring’s wider sections, says Morgado.
It is also possible that interactions between the ring’s particles or with Quaoar’s moon, Weywot, could be sustaining the ring. Further observations of Quaoar and more simulations of the system’s dynamics will be needed before a definitive answer can be found, says Morgado.Whatever the answer is, we might need to modify the Roche limit, which could have implications for other calculations in astrophysics.
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