© European Southern ObservatoryAn illustration shows the rings from the surface of the ice-rock centaur Chiron.
A distant comet trapped in orbit between Saturn and Uranus is accompanied by a transforming disk of icy dust, new observations reveal.A bizarre object that sometimes gets as close to the sun as Saturn, and other times retreats as far out as Uranus, has been discovered to have a transforming disk of dust around it that changes shape and can even mimic rings.
Minor planet 2060 Chiron is what's known as a Centaur, which are captured cometary objects that travel around the sun on looping orbits between Jupiter and Neptune. Chiron is just 218 kilometers (135 miles) across and occasionally has outbursts like a comet. To date, however, no spacecraft has ever visited a Centaur.
In 2011, Chiron passed in front of a faint star from our point of view here on Earth. Such events are referred to as "stellar occultations," and based on how an object such as Chiron blocks a star's light, the occulting object's shape and size can be determined through deduction. During the 2011 occultation, it was noticed that the star's light dimmed slightly — twice before Chiron itself occulted the star, and two further times after Chiron had moved past the star. This observation was interpreted as Chiron having a double-ring system of dust.
Then, Chiron occulted another star on Nov. 28, 2018, in an event taken advantage of by Amanda Sickafoose, who is a senior scientist at the Planetary Science Institute in Tucson, Arizona. Because Chiron's shadow cast by the star is so small, it crossed only a narrow region of the Earth, clipping southern Africa. Sickafoose therefore led a team who used the 1.9-meter (6.2 feet) telescope at the South African Astronomical Observatory in Sutherland, South Africa, to observe the occultation.
Their results, published exactly five years later, tell a slightly different story to 2011.
Comment: More studies on the Polistes fuscatus wasp species: