James Webb takes a closer look at asteroid 10199 Chariklo – Sciencetimes

What is asteroid Centaurus?

A centaur (or centaur, Centaurs) appears in Greek and Roman mythology and refers to a race with the upper half of a human being and the lower half of a horse. Thanks to this, the form in which two completely different qualities or appearances are combined is often compared to a centaur and named above. For example, there are several strains of coronavirus in BA. 2 and BA. BA has all 5 characteristics and is highly contagious. The 2.75 mutation is called the Centaurus mutation.

There are several asteroids whose orbits have long radii between the Jovian planets. They have long, highly distorted elliptical orbits, so they have long-period comets in distant orbits and asteroids in the asteroid belt in close orbits. Therefore, they were also nicknamed Centaurus by the Jet Propulsion Laboratory (JPL). Note that their orbits are unstable because they intersect more than once with the giant Jovian planets.

The asteroid Centaurus was first discovered in 1920 (944 Hidalgo), and later, in 1977, 2060 Chiron was discovered and began to be called a separate asteroid group. To date, it is estimated that there are at least 44,000 to more than 10,000,000 centaur asteroids in the solar system with a minimum diameter of more than 1 km in the solar system.

Do asteroids have rings like Jupiter and Saturn?

Of the many Centaur asteroid families, 10199 Chariklo is one of the most famous. The above asteroid is about 250 km in diameter (about 1/50 the diameter of Earth), boasting a similar size to the Asteroid Belt asteroids, and orbits between the orbits of Saturn and Uranus (about 3.2 billion km away from Saturn) . The asteroid above is famous because it has (very faint) rings like those of Jupiter and Saturn. This ring orbits the asteroid which is seen at a distance of about 400 km from the center of the main body.

In 2013, a team led by Dr Felipe Braga-Ribas used ground-based telescopes to observe Chariclo passing in front of the star. Amazingly, the star blinked twice before disappearing behind Chariclo, then flashed again. After appearing, it he blinked twice more. . These changes in star brightness are caused by Chariklo’s two thin rings, suggesting that the asteroid has a two-thin ring system. (Go to see relevant information)

Artist’s rendering of Curiclaw and double rings © NASA, ESA, CSA, Leah Hustak (STScI)

This discovery is the first to be found around small bodies, and has been recorded as a discovery of great interest because such rings were only expected to be found around large planets such as Jupiter, Saturn and Neptune. . So far, the direct external appearances of the above asteroid have not been photographed.

James Webb Conducts Successful Curiclo Circle Observations

James Webb observed the occultation of the above ring of asteroids passing in front of a background star. Dr Pablo Santos-Sanz of the Instituto de Astrofísica de Andalucía, Granada, Spain, observed occultations as part of the James Webb Space Telescope’s Guaranteed Time Observations (GTO) Solar System program, led by Dr Heidi Hammel. The “Target of Opportunity” approved a program (Program 1271) that seeks

This is because there are calculations and predictions that the Chariclo ring would show an occultation in October 2022. This is the first star-steroid ring occultation, first attempted by James Webb, in a very sophisticated observation. It’s a comment that would have been impossible if it weren’t for the closeness of James Webb, who prides himself on being extremely sensitive.

On October 18 last year, a research team led by Dr Hammel used the James Webb Space Telescope Near Infrared Camera (NIRCam) instrument to closely monitor the star Gaia DR3 6873519665992128512. Through this, it was discovered that an occultation phenomenon occurs along with a decrease in the brightness of the star, and it was confirmed that it was created by the Chariclo circle. The above results corresponded exactly to the predicted calculations and were recorded by the James Webb Space Telescope, a new way of searching for objects in the solar system. (see high resolution image)

James Webb conducts successful Curriclongny cycle observations. © NASA, ESA, CSA, L. Hustak (STScI), Pablo Santos-Sanz (IAA/CSIC), Nicolás Morales (IAA/CSIC), Bruno Morgado (UFRJ, ON/MCTI, LineA)

Dr Santos-Sants shows that these occultation light curves can be used to observe new scientific phenomena through James Webb, whose ring thickness, particle size and color (in astronomy, color is a specific wavelength) It was revealed that up to age of the term for whether it shines in the light) is noticeable. It is also predicted that it may be possible to observe new, weaker rings through this, and he explained that if these observations are accumulated, it will be possible to examine the origin of the rings.

Observations with the James Webb Space Telescope’s NIRCam instrument and an F150W filter (central wavelength 1.5 micrometres) revealed that the rings contained small frozen water particles mixed with the remains of ice bodies that collided with Cariclo in the past. The top of the graph shows a diagram showing the change in the position of the background stars relative to the icy body and its rings. The star appears to move behind the ring at two points along its path.

The graph below shows the change in relative brightness of the star between 9:33 and 9:41 am on October 18, 2022. That is, when the star is partially obscured by the ring, it showing two narrow, deep descending curves. This shows that the star did not go behind Chariklo, but passed behind Chariklo’s ring. This is because the brightness of the star shows a constant except when it appears to pass behind the rings.

Curiklo Surface Compositions, Crystalline Ice Discovered

Shortly after an occultation, James Webb observed Chariclo again, this time observing the light reflected from it and its rings (GTO Program 1272). The spectrum above shows the three absorption lines of water ice in the Curiclo system. He came out and explained that a number of observations were planned for the future. For example, it is expected that a wider understanding of the structure of Chariklo will be possible by understanding the change as the viewing angle of the circle changes.

© NASA, ESA, CSA, Leah Hustak (STScI), Noemí Pinilla-Alonso (FSI/UCF), Ian Wong (STScI), Javier Licandro (IAC)

The observations provide clear evidence of crystalline ice on the surface of Chariklo. An ice signature peak at around 3.2 micrometers is characteristic of both amorphous and crystalline ice, but the small peak at 1.6 micrometers only appears in crystalline ice.

James Webb’s sensitivity allowed him to distinguish this, which provides clues about ice movement. For example, amorphous ice is a form in which the molecules are not arranged, which is extremely rare on Earth but common in cryogenic space. This is because the temperature at which amorphous ice changes to crystalline ice varies depending on the environment (mainly pressure) of the celestial body, but it only changes to crystalline ice when the temperature is above a certain temperature . However, when the temperature is lowered again, it does not go back from amorphous to crystalline ice.

Through this, clues can be obtained about the evolution and movement of ice. In other words, it is the same as saying that Chariclo experienced a temperature higher than a certain temperature (about 130K), implying that it was not permanently outside the solar system. Because the Centaur asteroids have distorted orbital curves, they are predicted to have temperature environments consistent with the above findings.


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