The Centaurs, a group of asteroids located far beyond Saturn's orbit, is home to the largest among them, Chariklo. This rock, measuring 250 kilometers in diameter, is famous for its two narrow rings. The stellar occultation was the key to discovering Chariklo's two rings. This phenomenon occurs when an object blocks light from a distant star, causing a dip in its brightness.
Space.com mentioned that the scientists, including Felipe Braga-Ribas and his team, utilized this method to observe five dips in the light of a distant star while Chariklo passed in front of it - four from the rings and one from the asteroid. This technique has been used to uncover moons and study the solar system's atmospheres.
Crystallization on Chariklo
Researchers also aimed to repeat the process with the James Webb Space Telescope (JWST), and luck was on their side when a star aligned almost directly behind Chariklo last October. Although not perfectly aligned, only the rings covered the star. This was JWST's first successful stellar occultation, and it took place on Oct. 22nd, as reported by IFL Science.
Pablo Santos-Sanz from the Instituto de Astrofísica de Andalucía in Granada stated that as they continue to analyze the data, they will investigate the clear resolution of the two rings. By examining the shapes of the occultation light curves, they hope to uncover details about the rings' thickness, the size and color of the ring particles, and more. They hope to understand why Chariklo, a small body, has rings in the first place and potentially discover new, fainter rings.
The analysis of Chariklo is part of the Guaranteed Time Observations Program 1271, led by Santos-Sanz. The James Webb Space Telescope (JWST) also directly observed Chariklo and found evidence of water ice in a crystalline form. This indicates that the asteroid may have undergone small collisions, revealing deeper, pristine material or activating crystallization processes.
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Further Observation on Ring Changes
The presence of crystalline ice suggests ongoing activity, as high-energy particles can disrupt it, and thus seeing it suggests that either it is being formed or uncovered anew. JWST will keep observing Chariklo, and astronomers anticipate they will be able to differentiate more accurately between the asteroid and ring's contributions to the composition analysis in the future.
Most of the light in the spectrum is reflected by Chariklo itself. Models estimate that the observed ring area seen from the James Webb Space Telescope (Webb) during the observations is likely one-fifth the size of the asteroid's body. With its high sensitivity and detailed models, Webb may be able to distinguish the ring's material from Chariklo's. Observing Chariklo with Webb over several years as the rings' angle changes, the rings' contribution may be isolated.
The successful observation of Chariklo by the James Webb Space Telescope opens the door for new ways to analyze small objects in the far reaches of the solar system. With its high sensitivity and infrared capability, scientists can utilize the unique information provided by these occultations and combine it with contemporaneous spectra. These tools will be invaluable for scientists studying distant small bodies in our solar system.
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