James Webb Space Telescope finds water ice in rings of an asteroid

NASA’s James Webb Space telescope has found water ice in the ring of a distant object in our solar system, but it’s not Saturn with its remarkable rings, or Neptune, Uranus or even Jupiter which has rings which are too faint to be seen by most telescopes.

The fifth ringed object in our solar system is the asteroid Chariklo which was  discovered in 1997, but it wasn’t until 2013 that scientists using ground-based telescopes found that Chariklo is the first asteroid to have a ring system.

Chariklo is a small, icy body about 3.2 million kms beyond the orbit of Saturn. At around 300 kilometres in diameter, the asteroid is the largest known object in the Centaur population – a group asteroids (estimated between 44,000 and more than 10 million objects).

The asteroid has two thin rings which orbit at a distance of about 400 kilometres from Chariklo’s centre.

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This video shows observations taken by NASA’s James Webb Space Telescope of a star (fixed in the center of the video) as Chariklo passes in front of it. Credit: NASA, ESA, CSA, Nicolás Morales (IAA/CSIC).

An analysis suggests the rings are probably composed of small particles of water ice mixed with a darker material – probably the remnant of an icy body which collided with Chariklo in the past.

An occultation light curve from Webb’s Near-infrared Camera (NIRCam) Instrument. As seen in the illustration of the occultation event, the star did not pass behind Chariklo from Webb’s viewpoint, but it did pass behind its rings. Credit: NASA, ESA, CSA, Leah Hustak (STScI). Science: Pablo Santos-Sanz (IAA/CSIC), Nicolás Morales (IAA/CSIC), Bruno Morgado (UFRJ, ON/MCTI, LIneA).

“Spectra from ground-based telescopes had hinted at this ice, but the exquisite quality of the James Webb telescope spectrum revealed the clear signature of crystalline ice for the first time” says project lead Dr Noemí Pinilla-Alonso from the Florida Space Institute at the University of Central Florida.

Webb captured a spectrum with its Near-infrared Spectrograph (NIRSpec) of the Chariklo system on Oct. 31, shortly after the occultation. This spectrum shows clear evidence for crystalline water ice. Credit: NASA, ESA, CSA, Leah Hustak (STScI).

“Because high-energy particles transform ice from crystalline into amorphous states, detection of crystalline ice indicates that the Chariklo system experiences continuous micro-collisions that either expose pristine material or trigger crystallization processes,” adds Dr Dean Hines from Baltimore’s Space Telescope Science Institute, principal investigator of the Chariklo spectral analysis program.

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