Webb Telescope Reveals Centaur Chariklo's Thin Rings in High Precision Observation
The AO Editors
This artist's rendering depicts the appearance of Chariklo's rings as seen from the surface of the centaur, a small solar system object that straddles the line between asteroid and comet.
NASA/JPL-Caltech
Scientists captured the shadows of starlight cast by the thin rings of Chariklo, a small icy body beyond Saturn's orbit, using NASA's James Webb Space Telescope. Chariklo, the largest known Centaur, is located over 2 billion miles from Earth and is only 51 times smaller in diameter than the planet. Its rings orbit the body at a distance of approximately 400 kilometers (250 miles).
On October 18, 2022, Chariklo (center) passed in front of a background star. James Webb Space Telescope captured 63 separate observations of the phenomenon known as a stellar occultation. The brief dimming of light just before the star passes behind Chariklo is caused by his rings.
NASA/ESA/CSA/Nicolás Morales (IAA/CSIC).
Using ground-based telescopes, astronomers unexpectedly discovered Chariklo's system of two thin rings in 2013. Previously, rings had only been observed around giant planets such as Jupiter and Neptune. Astronomers observed Chariklo pass in front of a star, blocking its light, and noticed the star blinking on and off twice before vanishing behind the planet. After the star reemerged, it double-blinked again, revealing the presence of two thin rings - the first rings ever discovered around a small solar system object.
Using Webb's Near-Infrared Camera (NIRCam), a team led by Pablo Santos-Sanz of the Instituto de Astrofsica de Andaluca in Granada, Spain, observed an occultation event. Chariklo was determined to be on track for an occultation event in October 2022, the first stellar occultation event attempted with Webb. By observing the star Gaia DR3 6873519665992128512, scientists were able to detect the shadows cast by Chariklo's rings with great precision.
This graphic shows the path the background star took behind Chariklo’s rings, nearly passing directly behind the centaur itself. As the star passed behind the rings, its brightness dipped.
NASA, ESA, CSA, Leah Hustak (STScI) SCIENCE: Pablo Santos-Sanz (IAA-CSIC), Nicolás Morales (IAA-CSIC)
The Webb occultation light curve, a graph depicting an object's brightness over time, indicated that the observations were successful. The shadows of the rings were captured exactly as predicted, and the light- -curves will provide new scientific insights into the ring's properties. Santos-Sanz hopes to determine if the team successfully resolved the two rings and if there are additional, fainter rings.
NASA, ESA, CSA, Leah Hustak (STScI). Science: Noemí Pinilla-Alonso (FSI/UCF), Ian Wong (STScI), Javier Licandro (IAC)
Chariklo's rings are likely composed of small particles of water ice mixed with dark material, debris from an icy body that previously collided with Chariklo. Because Chariklo is too small and distant for the Webb telescope to directly image the rings separated from the main body, occultations are the only way to observe the rings on their own. This ground-breaking observation demonstrates a new way to explore solar system objects with Webb and opens up new avenues for understanding the formation of small bodies in our solar system.
