A team of astronomers from MIT have detected signs of a possible ring system around the minor planet Chiron. First discovered in 1977, Chiron belongs to a class of minor planets known as centaurs. These bodies share some of the characteristics exhibited by both comets and asteroids, hence their classification as Centaurs, which in ancient mythology denoted a creature with the traits of both man and horse.
Astronomers estimate that there are in excess of 44,000 centaurs present in our solar system, mostly existing in the space between the orbits of Jupiter and Pluto. One such centaur, Chariklo, has already been found to host a ring system of its own. The discovery shocked astronomers, as it was not previously thought that so small a body had sufficient gravity to capture the materials to form its own ring system.
The recent observations of Chiron were made using two Hawaii-based observatories – NASA's Infrared Telescope Facility located on Mauna Kea, and the Las Cunbres Observatory Global Telescope Network, Haleakala. The telescopes were tasked with watching for a stellar occultation, which occurs when a body, in this case Chiron, passes in front of a bright, distant star.
"There's an aspect of serendipity to these observations," states Amanda Bosh, lecturer in MIT's Department of Earth, Atmospheric and Planetary Sciences. "We need a certain amount of luck, waiting for Chiron to pass in front of a star that is bright enough. Chiron itself is small enough that the event is very short; if you blink, you might miss it."
The team had only a few short minutes to gather data on the centaur before it slipped past the disk of the star, and returned to the dark backdrop of deep space. Analysis of the data showed symmetrical features roughly 300 km (186 miles) either side of Chiron. The first feature to be detected is believed to be around 3 km (1.8 miles) wide, while the trailing feature is around 7 km (4 miles) wide. The features are believed to be indicative of dust or gas blocking some of the light from the star.
The team cannot yet say for certain whether the unusual readings are indeed the markers of a ring system around Chiron. Other possible explanations of the symmetrical readings include jets of gas and dust, or even a shell composed of the same materials. Either way, the findings represent a surprising level of activity when compared to what was expected.
Further observations of Chiron during a stellar occultation will be required to determine the nature of the phenomenon causing the unexpected readings.