The James Webb Space Telescope has allowed scientists to study the occultation of a distant star by the rings of the centaur Chariklo. This asteroid is located between the orbits of Saturn and Uranus. New research shows that the material orbiting around it is undergoing constant changes.
The Rings of Chariklo
According to phys.org, a study published in Science Advances claims that the rings of the asteroid Chariklo have changed significantly in just a few years. This conclusion was reached after observations with the James Webb Space Telescope.
Just 20 years ago, scientists thought that only giant planets had rings. But later, rings began to be discovered around relatively small objects orbiting the Sun far from it. One of them was Chariklo, which belongs to the class of centaurs. This is the name given to asteroids that orbit between the orbits of the giant planets.
In the case of Chariklo, which is about 258 km in diameter, the rings interact with the gravity of Saturn and Uranus. They were discovered back in 2013 by observing how Chariklo occulted a star. Two rings were found: one has a diameter of 396 km, while the other is 405 km across. In 2022, James Webb already observed a stellar occultation, which made it possible to determine the optical density of the rings.
James Webb Observations
Now a new study has appeared, based on a new observation of a stellar occultation using the James Webb Space Telescope. It is located at the L2 Lagrange point, in Earth’s shadow, and therefore can see many interesting details with its infrared cameras.
This time, the space telescope was very fortunate. At the moment when Chariklo passed between it and a distant star, the relative velocity was only 2.5 km/s. This made it possible to carry out very precise observations. The result turned out to be surprising. The larger ring, which is closer to Chariklo, proved to be denser than in the previous study, while the more distant ring, on the contrary, was more diffuse.
And this is not an observational inaccuracy. The characteristics of the rings changed in just a few years, and scientists do not know what caused it. They suspect that the reason may be that the material orbiting Chariklo is actually something more complex than simply a ring.
