. 24/7 Space News .
OUTER PLANETS
Webb spies Chariklo ring system with high-precision technique
by Thaddeus Cesari for NASA Blogs
Baltimore MD (SPX) Jan 26, 2023

An occultation light curve from Webb's Near-infrared Camera (NIRCam) Instrument at 1.5 microns wavelength (F150W) shows the dips in brightness of the star (Gaia DR3 6873519665992128512) as Chariklo's rings passed in front of it on Oct. 18. 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. Each dip actually corresponds to the shadows of two rings around Chariklo, which are ~4 miles (6-7 kilometers) and ~2 miles (2-4 kilometers) wide, and separated by a gap of 5.5 miles (9 kilometers). The two individual rings are not fully resolved in each dip in this light curve. Image credit: NASA, ESA, CSA, Leah Hustak (STScI). Science: Pablo Santos-Sanz (IAA/CSIC), Nicolas Morales (IAA/CSIC), Bruno Morgado (UFRJ, ON/MCTI, LIneA). Infographic here and additional images and detailed captions are here

In an observational feat of high precision, scientists used a new technique with NASA's James Webb Space Telescope to capture the shadows of starlight cast by the thin rings of Chariklo. Chariklo is an icy, small body, but the largest of the known Centaur population, located more than 2 billion miles away beyond the orbit of Saturn. Chariklo is only 160 miles (250 kilometers) or ~51 times smaller than Earth in diameter, and its rings orbit at a distance of about 250 miles (400 kilometers) from the center of the body.

We asked members of the science team observing Chariklo to tell us more about this unique system, the occultation technique, and what they learned from their Webb observations.

In 2013, Felipe Braga-Ribas and collaborators, using ground-based telescopes, discovered that Chariklo hosts a system of two thin rings. Such rings had been expected only around large planets such as Jupiter and Neptune. The astronomers had been watching a star as Chariklo passed in front of it, blocking the starlight as they had predicted. Astronomers call this phenomenon an occultation. To their surprise, the star blinked off and on again twice before disappearing behind Chariklo, and double-blinked again after the star reemerged. The blinking was caused by two thin rings - the first rings ever detected around a small solar system object.

Pablo Santos-Sanz, from Instituto de Astrofisica de Andalucia in Granada, Spain, has an approved "Target of Opportunity" program (program 1271) to attempt an occultation observation as part of Webb's solar system Guaranteed Time Observations (GTO) led by Heidi Hammel from the Association of Universities for Research in Astronomy. By remarkable good luck, we discovered that Chariklo was on track for just such an occultation event in October 2022. This was the first stellar occultation attempted with Webb. A lot of hard work went into identifying and refining the predictions for this unusual event.

On Oct. 18, we used Webb's Near-Infrared Camera (NIRCam) instrument to closely monitor the star Gaia DR3 6873519665992128512, and watch for the tell-tale dips in brightness indicating an occultation had taken place. The shadows produced by Chariklo's rings were clearly detected, demonstrating a new way of using Webb to explore solar system objects. The star shadow due to Chariklo itself tracked just out of Webb's view. This appulse (the technical name for a close pass with no occultation) was exactly as had been predicted after the last Webb course trajectory maneuver.

The Webb occultation light curve, a graph of an object's brightness over time, revealed that the observations were successful! The rings were captured exactly as predicted. The occultation light curves will yield interesting new science for Chariklo's rings. Santos-Sanz explained: "As we delve deeper into the data, we will explore whether we cleanly resolve the two rings. From the shapes of rings' occultation light curves, we also will explore the rings' thickness, the sizes and colors of the ring particles, and more. We hope gain insight into why this small body even has rings at all, and perhaps detect new fainter rings."

The rings are probably composed of small particles of water ice mixed with dark material, debris from an icy body that collided with Chariklo in the past. Chariklo is too small and too far away for even Webb to directly image the rings separated from the main body, so occultations are the only tool to characterize the rings by themselves.

Precision Technique
Editor's Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process.

In an observational feat of high precision, scientists used a new technique with NASA's James Webb Space Telescope to capture the shadows of starlight cast by the thin rings of Chariklo. Chariklo is an icy, small body, but the largest of the known Centaur population, located more than 2 billion miles away beyond the orbit of Saturn. Chariklo is only 160 miles (250 kilometers) or ~51 times smaller than Earth in diameter, and its rings orbit at a distance of about 250 miles (400 kilometers) from the center of the body.

We asked members of the science team observing Chariklo to tell us more about this unique system, the occultation technique, and what they learned from their Webb observations.

In 2013, Felipe Braga-Ribas and collaborators, using ground-based telescopes, discovered that Chariklo hosts a system of two thin rings. Such rings had been expected only around large planets such as Jupiter and Neptune. The astronomers had been watching a star as Chariklo passed in front of it, blocking the starlight as they had predicted. Astronomers call this phenomenon an occultation. To their surprise, the star blinked off and on again twice before disappearing behind Chariklo, and double-blinked again after the star reemerged. The blinking was caused by two thin rings - the first rings ever detected around a small solar system object.

Pablo Santos-Sanz, from Instituto de Astrofisica de Andalucia in Granada, Spain, has an approved "Target of Opportunity" program (program 1271) to attempt an occultation observation as part of Webb's solar system Guaranteed Time Observations (GTO) led by Heidi Hammel from the Association of Universities for Research in Astronomy. By remarkable good luck, we discovered that Chariklo was on track for just such an occultation event in October 2022. This was the first stellar occultation attempted with Webb. A lot of hard work went into identifying and refining the predictions for this unusual event.

On Oct. 18, we used Webb's Near-Infrared Camera (NIRCam) instrument to closely monitor the star Gaia DR3 6873519665992128512, and watch for the tell-tale dips in brightness indicating an occultation had taken place. The shadows produced by Chariklo's rings were clearly detected, demonstrating a new way of using Webb to explore solar system objects. The star shadow due to Chariklo itself tracked just out of Webb's view. This appulse (the technical name for a close pass with no occultation) was exactly as had been predicted after the last Webb course trajectory maneuver.

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. The video is composed of 63 individual observations with Webb's Near-infrared Camera Instrument's view at 1.5 microns wavelength (F150W) obtained over ~1 hour on Oct. 18. Careful analysis of the star's brightness reveals that the rings of the Chariklo system were clearly detected. Credit: NASA, ESA, CSA, Nicolas Morales (IAA/CSIC)

The Webb occultation light curve, a graph of an object's brightness over time, revealed that the observations were successful! The rings were captured exactly as predicted. The occultation light curves will yield interesting new science for Chariklo's rings.

Santos-Sanz explained: "As we delve deeper into the data, we will explore whether we cleanly resolve the two rings. From the shapes of rings' occultation light curves, we also will explore the rings' thickness, the sizes and colors of the ring particles, and more. We hope gain insight into why this small body even has rings at all, and perhaps detect new fainter rings."

The rings are probably composed of small particles of water ice mixed with dark material, debris from an icy body that collided with Chariklo in the past. Chariklo is too small and too far away for even Webb to directly image the rings separated from the main body, so occultations are the only tool to characterize the rings by themselves.

An occultation light curve from Webb's Near-infrared Camera (NIRCam) Instrument at 1.5 microns wavelength (F150W) shows the dips in brightness of the star (Gaia DR3 6873519665992128512) as Chariklo's rings passed in front of it on Oct. 18. 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.

Each dip actually corresponds to the shadows of two rings around Chariklo, which are ~4 miles (6-7 kilometers) and ~2 miles (2-4 kilometers) wide, and separated by a gap of 5.5 miles (9 kilometers). The two individual rings are not fully resolved in each dip in this light curve. Image credit: NASA, ESA, CSA, Leah Hustak (STScI). Science: Pablo Santos-Sanz (IAA/CSIC), Nicolas Morales (IAA/CSIC), Bruno Morgado (UFRJ, ON/MCTI, LIneA). Download the full-resolution version from the Space Telescope Science Institute.

Shortly after the occultation, Webb targeted Chariklo again, this time to collect observations of the sunlight reflected by Chariklo and its rings (GTO Program 1272). The spectrum of the system shows three absorption bands of water ice in the Chariklo system. Noemi Pinilla-Alonso, who led Webb's spectroscopic observations of Chariklo, explained: "Spectra from ground-based telescopes had hinted at this ice (Duffard et al. 2014), but the exquisite quality of the Webb spectrum revealed the clear signature of crystalline ice for the first time."

Dean Hines, the principal investigator of this second GTO program, added: "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."

Most of the reflected light in the spectrum is from Chariklo itself: Models suggest the observed ring area as seen from Webb during these observations is likely one-fifth the area of the body itself. Webb's high sensitivity, in combination with detailed models, may permit us to tease out the signature of the ring material distinct from that of Chariklo. Pinilla-Alonso commented that "by observing Chariklo with Webb over several years as the viewing angle of the rings changes, we may be able to isolate the contribution from the rings themselves."

Our successful Webb occultation light curve and spectroscopic observations of Chariklo open the door to a new means of characterizing small objects in the distant solar system in the coming years. With Webb's high sensitivity and infrared capability, scientists can use the unique science return offered by occultations, and enhance these measurements with near-contemporaneous spectra. Such tools will be tremendous assets to the scientists studying distant small bodies in our solar system.

About the authors:

Heidi B. Hammel is a Webb interdisciplinary scientist leading Webb's Cycle 1 Guaranteed Time Observations (GTO) of the solar system, including Program 1271 as highlighted here. She is the vice president for science at the Association of Universities for Research in Astronomy (AURA) in Washington, D.C.

Dean Hines is an observatory scientist at the Space Telescope Science Institute (STScI) in Baltimore, Maryland and part of Webb's Mid-infrared Instrument Team. He is the principal investigator for Webb's Guaranteed Time Observations Program 1272 "Kuiper Belt Science with JWST."

Noemi Pinilla-Alonso is an associate scientist in planetary science at the Florida Space Institute at the University of Central Florida and deputy principal scientist for the Arecibo Observatory. She is leading the science analysis of the Chariklo system's spectrum obtained by Webb's Near-infrared Spectrograph.

Pablo Santos-Sanz is a planetary scientist at the Instituto de Astrofisica de Andalucia (CSIC) and director of the Sierra Nevada Observatory in Granada, Spain. He is the principal investigator for Webb's Guaranteed Time Observations Program 1271 "ToO TNOs: Unveiling the Kuiper belt by stellar occultations."


Related Links
James Webb Space Telescope
The million outer planets of a star called Sol


Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Monthly Supporter
$5+ Billed Monthly


paypal only
SpaceDaily Contributor
$5 Billed Once


credit card or paypal


OUTER PLANETS
Exotic water ice contributes to understanding of magnetic anomalies on Neptune and Uranus
Sao Paulo, Brazil (SPX) Jan 23, 2023
Ordinary everyday ice, like the ice produced by a fridge, is known to scientists as hexagonal ice (ice Ih), and is not the only crystalline phase of water. More than 20 different phases are possible. One of them, called "superionic ice" or "ice XVIII", is of particular interest, among other reasons, because it is thought to make up a large part of Neptune and Uranus, planets frequently referred to as "ice giants". In the superionic crystalline phase, water loses its molecular identity (H2O): negat ... read more

Comment using your Disqus, Facebook, Google or Twitter login.



Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

OUTER PLANETS
UAE astronaut says not required to fast during Ramadan on ISS

20 Years Ago: Remembering Columbia and Her Crew

NASA selects nine technologies for commercial flight tests

Astronauts conduct first ISS spacewalk of 2023

OUTER PLANETS
NASA safety system enables Rocket Lab launch from Wallops

NASA validates revolutionary propulsion design for deep space missions

Isar Aerospace and Spaceflight Inc sign launch agreement to service global market

NASA, Boeing teams achieve milestone ahead of crewed flight

OUTER PLANETS
Searching for buried treasure on Mars with RIMFAX

Aiming for the Triple Junction: Sols 3723-3724

Sol 3721: Wrapping up at the Encanto Drill Site

NASA launches Mars Sample Receiving Project Office at Johnson

OUTER PLANETS
Chinese astronauts send Spring Festival greetings from space station

China to launch 200-plus spacecraft in 2023

China's space industry hits new heights

China's first private sector 2023 rocket launch up, up and away

OUTER PLANETS
How ESA works with the EU to advance European space

SpaceX launches 56 more Starlink satellites in heaviest payload yet

Hawkeye 360 launches Cluster 6 satellites aboard inaugural Rocket Lab Electron flight from Virginia

UK Space Agency announces new funding for satellite communications

OUTER PLANETS
The last mysteries of mica

Novel technique developed to obtain key chemical industry input without emitting CO2

Temperature-sensing building material changes color to save energy

MLU physicists solve mystery of two-dimensional quasicrystal formation from metal oxides

OUTER PLANETS
Webb Telescope identifies origins of icy building blocks of life

Rare opportunity to study short-lived volcanic island reveals sulfur-metabolizing microbes

New small laser device can help detect signs of life on other planets

How do rocky planets really form

OUTER PLANETS
NASA's Juno Team assessing camera after 48th flyby of Jupiter

Webb spies Chariklo ring system with high-precision technique

Europe's JUICE spacecraft ready to explore Jupiter's icy moons

Exotic water ice contributes to understanding of magnetic anomalies on Neptune and Uranus









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.