Astronomers Have Discovered Rings Around A Miniature Planet Between Saturn And Uranus

Chariklo is a comet-like miniature planet located between Saturn and Uranus. It has a diameter of 250 km and new observations show that there are two rings of ice particles and pebbles. This is the first time such a small celestial body with rings has been observed. Image: Lucie Maquet

A miniature planet called Chariklo about two billion kilometers out in the solar system between Saturn and Uranus has been found to have rings.

Until now, rings have only been observed around giant planets such as Jupiter, Uranus, Neptune and especially Saturn.

Results of observations by astronomers from the Niels Bohr Institute are published today in the journal Nature.

This comet-like object with a diameter of 250 kilometres has been known for many years but despite careful study its rings have not been observed before now. This has happened because a new camera is now being used on the Danish telescope at ESO’s La Silla Observatory in Chile.

“The camera was specially developed at the Niels Bohr Institute and has a stunningly high resolution, which we especially exploit to look for exoplanets,” says Uffe Gråe Jørgensen, an astronomer in Astrophysics and Planetary Science at the Niels Bohr Institute at the University of Copenhagen.

“But when the area where we are looking for exoplanets isn’t ‘up’ in the sky, we use our observation time for other projects and so we followed Chariklo, which just passed in front of a star.”

When an object passes in front of a star there is a small dip in the star’s brightness and they could see that there was also a dip in the brightness outside the object. This showed there was a ring of material in a disc around the little object, Chariklo.

Uffe Gråe Jørgensen says:

“We were not even looking for rings, because they had never been observed around small objects like Chariklo, so it is a totally surprising discovery. The entire passage only lasted 5 seconds, but we could even determine incredible details about the rings. There are two separate thin rings, which are comprised of ice particles and pebbles. The two rings are only 3 km and 7 km wide and no more than a few hundred metres thick. There are 14 km between the centers of the two rings and there is a 9 km wide gap between them. They have been measured at a distance of two billion kilometers with an accuracy of plus/minus a few hundred meters. It is really impressive.”

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