"Astronomers have spotted a ring around a dwarf planet called Quaoar in the
outer reaches of the solar system.
The observations, by a powerful telescope on La Palma, reveal the ring to be
much further away from the planet than is typical, calling into question how
such systems form.
Prof Vik Dhillon, of the University of Sheffield’s department of physics and
astronomy, and his co-authors, said: “The ring came as a real surprise and
doubly surprising was where it was, well outside the theoretical maximum for
where a ring can survive according to classical theory. These are the most
unusual rings we’ve seen.”
The dwarf planet, which is about half the size of Pluto and orbits beyond
Neptune, is too distant and the ring too narrow to be seen directly. The
detection was made during a so-called occultation event, when a planet passes
directly in front of a star, meaning its sharp silhouette can be briefly
observed by Earth-based telescopes.
“Astronomers who work in this area predict these occultations to the second,
years in advance,” said Dhillon. “One of these was predicted and we were on the
observatory on La Palma.”
The observations, by the HiPERCAM telescope, showed a sharp dip in starlight as
Quaoar passed in front of the star. Intriguingly, two smaller dips, before and
after, were also observed, which the astronomers realised indicated the
presence of a ring system."
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