Similarities with the moon

Furthermore, the collision that created the rings is reminiscent of the most likely hypothesis explaining the formation of the moon. There could indeed have been a collision between a small planet and Earth when it was formed. Material could have been torn off and put into orbit in the form of a ring around our planet. This disk would then have been compressed and turned into the moon. “However, Chariklo’s rings aren’t going to form a satellite, any more than Saturn's rings", the researcher adds.  “When the moon was formed, the material in the solar system was still very hot and the rocks were malleable. Today, the material is too cold. What’s more, the majority of asteroids aren’t very compact. You could almost consider them as big piles of stones.”

An eye on the ring

This double ring is therefore a true discovery that no-one was expecting. Like all discoveries, it opens a new chapter in the study of small solar system bodies. What is the stability of these rings, how did they appear, from what material are they composed, are they confined by shepherd satellites, or is it necessary to review the whole theory explaining the rings’ gravitational, even planetary,  stability, are there other small bodies equipped with these sorts of rings? “Before, we weren’t particularly looking for them. Now, we’re going to", the delighted researcher tells us. “It was difficult to make these observations, especially because it isn't easy to predict occultations. We still miss the majority of them. We can’t even observe them because the eclipse doesn’t occur above our telescopes. But now we know what we’re looking for and we’re going to work on it. For the other asteroids, but also for Chariklo.”


TRAPPIST is such a success story that the researchers from ULg have asked for funds to build its little brother in the northern hemisphere, thus giving us the ability to cover the entire sky from Earth. However, the telescope wasn’t designed to observe these occultations. Its primary missions are to detect exoplanets and study the chemical composition of comets and asteroids, to which the researchers devote the majority of the telescope’s time. That said, the observation of Chariklo wasn’t a first attempt. The researchers endeavour to detect occultations approximately every month, and it is the third time that an occultation has been a determining factor in the domain, and the subject of an article in the journal Nature et Science. Thanks to TRAPPIST, it was possible to precisely measure the size of Eris (read the article Eris, Pluto’s distant twin), considered the possible tenth planet for a while. Emmanuël Jehin and his colleagues now have every intention of stepping up their programme around this type of object. TRAPPIST will observe Chariklo once a week, in particular to detect possible comet-like activity. No need for the occultation of a star, the asteroid's direct light is sufficient for this type of observation.

And the telescope from Liège isn’t of course the only one looking at the Centaur. From initially being quite run-of-the-mill, it has become the darling of astrophysicists in less than a year, and is currently enjoying such a level of interest that the biggest telescopes in the world, requisitioned for leading missions, may well deign to have a little peek. “Chariklo has become a unique object in the solar system”, the researcher boasts. “The information that this unique object will reveal, in particular concerning its chemical composition, its activity and its stability, are crucial. Since the discovery of these two rings, several study projects have been submitted. For instance, an application for observations was introduced to use NASA's Hubble space telescope. With such a sensitive instrument, and with the clarity of the observations made from space, without the terrestrial atmosphere, it might be possible to observe the rings directly. Now we’ve found this system, we’re not going to let it go.”