I like this asteroid and therefore put a ring on it. This image is an artist’s impression of t
I like this asteroid and therefore put a ring on it. This image is an artist’s impression of the asteroid Chariklo, which turns out to be a remarkable object in the outer solar system – it has RINGS!This tiny object is only about 250 kilometers wide – comparable in size to the nation of Switzerland, but it joins the 4 giant planets (Jupiter, Saturn, Uranus, and Neptune) as the 5th object in the solar system to have rings.10199 Chariklo (the number indicates order of discovery) is a Centaur, part of a population of asteroids between Saturn and Uranus. It is so far out that it can only be seen as a faint point of light from earth; many properties like its size are difficult to determine without a specific measurement called an occultation.Its orbit is known well enough that in 2013, it was projected to pass between Earth and the star UCAC4 248-108672. When an asteroid passes between a star and the Earth, it blocks out the light of that star temporarily, and the amount of time that passes can be turned into the size of the object.In June of 2013, telescopes including the 1.54-metre Danish and TRAPPIST telescopes at ESO’s La Silla Observatory in Chile pointed their lenses towards the asteroid as it occulted the star, but they saw something funny – there were tiny dims before and after the object passed.This asteroid has something else around it, making a symmetrical pattern on either side. That means… Chariklo has 2 narrow rings around it! The rings themselves are about 7 and 3 kilometers wide, with a 9 kilometer gap between them. This technique is actually the same one used to discover the rings around Uranus and Neptune decades ago.Even more interesting, these rings are actually very thin; interactions within the rings typically would cause them to spread out. The sharpness of the rings and the sharp gap within suggests that there must be other gravity sources in the system to sculpt the rings – almost certainly indicating that Chariklo has both rings and moons! It’s practically a mini-Saturn!The project was led by a scientist from Brazil’s Observatório Nacional and therefore, the 2 rings are known colloquially as Oiapoque and Chuí after 2 rivers in Brazil.With this many objects in the system, the obvious explanation is that Chariklo at some point suffered an impact with a fast-moving body that sprayed debris from it into the surround space. There are other ways for asteroids to create moons, if the sun’s energy heats one side of the asteroid causing it to spin, but this asteroid is so far out the sun’s impact on it should be small. Interestingly though, the area of the solar system containing the centaurs has vastly fewer asteroids than the main belt of asteroids between Mars and Jupiter, so if these rings were produced by impact, they may tell an interesting and surprising story about collisions in the outer solar system.It’s really interesting to wonder how a tiny object like this had strong enough gravity to hold onto so much debris from the impact; figuring out how a tiny asteroid can not only survive an impact but sculpt the debris into rings seems like a fun challenge for physicists and a logical next step in this research.Anyway, I guess the next question is…can we go there and see what they actually look like? Image credit: ESO -- source link