The celestial bodies known as centaurs are rocky dwarf planets situated in the middle section of the Solar System (between Jupiter and Pluto), which possess the attributes of both asteroids and comets. Centaurs were thought to be dormant spatial objects, but almost a year ago (on March 26, 2014, to be precise), scientists spotted two rings around Chariklo, the largest of centaurs in our solar system (named after a nymph in Greek mythology, centaur Chiron’s wife). Now, it has been confirmed that Chiron, another centaur from the middle Solar System, possesses a ring system. This conclusion is based on the observation of a stellar occultation (Chiron passed in front of a bright star in 2011, and the analysis of its shadow and other optical features led to the conclusion that it has rings around it).
Discovered in 1977, Chiron (named after a healer mythological centaur that was said to have taught Achilles, Perseus, or Jason) is one of the approximately 44,000 centaurs in the solar system. MIT scientist James Elliot was the first one to estimate its size (back in 1993), and to observe its comet-like behavior (emanating jets of water and dust, the dwarf planet was not as dormant as it had appeared).
Amanda Bosh, a lecturer in MIT’s Department of Earth, Atmospheric and Planetary Sciences, says that the discovery is all the more interesting given that the area between Jupiter and Pluto had been previously considered inactive. According to this researcher, observations like this require “an aspect of serendipity” and “a certain amount of luck”, because the dwarf planet is small enough and far enough for events like its passing by a very bright star to be quite brief and quite seldom. Although one can miss an event such as this in the blink of an eye, researchers did not miss it because they had prepared for it. They had calculated, by charting Chiron’s orbit, that on November 29, 2011, the centaur would pass in front of a star and they had planned to observe it. What they saw, along with the dwarf planet’s shadow, was a set of symmetrical, sharp features at a distance of 300 km from its surface. The most plausible explanation for this is that the minor planet has rings, which makes sense if we accept the hypothesis that another small celestial body broke up near Chiron, and the centaur’s gravitational field attracted the debris.
An independent group of researchers has reached the same conclusions with the MIT astrophysicists, but nevertheless specialists say that more observations are required before taking this for granted. MIT researcher Jessica Ruprecht considers that to verify the ring hypothesis multiple observations from different points distributed over hundreds of kilometers are needed.
Assuming the MIT group’s theories are not infirmed in the future, Chiron is officially the sixth ringed object in the Solar System, after Saturn, Uranus, Neptune, Jupiter, and Chariklo.