The giant planet Saturn isn’t the only marred world in the solar system. Uranus, Neptune and even Jupiter also have rings, but there is also a small world two billion miles from Earth called 10199 Chariklo – as now proven by the James Webb Space Telescope.
First discovered in 1997, it is an icy asteroid, which is one of the building blocks of the solar system, but is also known as a minor planet. Either way, it is the smallest known planetary body with rings.
Measuring about 146 miles/235 km in diameter—nearly half the length of the Grand Canyon and twice the width of the English Channel—Chariklo is a centaur, an asteroid orbiting the sun farthest from Jupiter and Neptune.
It’s the largest centaur we’ve discovered so far, but from a telescope standpoint it’s very small, far away, and dark. So there is only one way to detect them – starlight.
Astronomers have known for nearly a decade that Chariklo has rings. A pair of narrow glacier water loops, one four miles/seven kilometers wide and the other two miles/three kilometers wide. Its rings orbit about 250 miles (400 kilometers) from the object’s center.
This was discovered using telescopes at the European Southern Observatory (ESO) in La Silla, Chile, which observed Chariklo’s motion in front of a star. The light of the background star illuminated Chariclo for a moment, just enough to reveal his rings.
A similar feat was accomplished using JWST, which on October 18, 2022 captured the star shadows cast by Chariklo’s thin rings as it drifted in front of a star. It is the only way to study Chariklo, and it is very dim and far from the picture directly.
Using JWST’s Near Infrared Camera Instrument (NIRCam), shadows produced by Chariklo’s rings were clearly detected in the light curve, which is a graph of the object’s brightness over time. From the shapes of the light curves of the rings, the researchers hope to determine their thickness, size and colors – and perhaps even new, fainter rings.
Like most centaurs, Chariklo is not in a stable orbit, comfortably traveling from beyond Saturn into the distance of Uranus during one trip around the Sun, which takes about 63 Earth years to complete.
I wish you clear skies and wide eyes.