Neptune’s rings, flown over by Voyager 2
Neptune’s rings were first photographed in 1989, when the Voyager 2 spacecraft passed close to the ice giant. Voyager 2, launched on August 20, 1977, is to date the only spacecraft to have come close to the planet Neptune.
The existence of a system of rings revolving around Neptune has been mentioned since 1846 when the British astronomer William Lassel thought he saw at least one ring around the planet. This scientist was also the discoverer of Triton, Neptune’s largest moon. In 1968, one of the planet’s rings was revealed thanks to the stellar occultation technique used to detect objects in the solar system that are too small, too faint, or too distant. The technique consists of capturing the image of the object as it passes in front of a star. Then the stellar luminous flux is analyzed.
In 1984, the first tangible evidence for the existence of Neptune’s rings came during a star occultation observing program at ESO’s La Silla Observatory in northern Chile. At this time, astronomers are certain of the presence of something around Neptune that they consider to be incomplete arcs.
The Voyager 2 probe definitively proved the existence of the rings. Later, the Hubble Space Telescope also contributed to this discovery.
Currently, astronomers know of the existence of five rings that orbit around Neptune. Three of them have a width that does not exceed 100 km and the other two have a width between 2,000 and 5,000 km. Neptune’s rings are made mostly of very fine dust.
(Also read: James Webb: behind the scenes of a historical photo!)
Neptune’s rings and the seven moons.
This image shows Neptune’s rings and seven moons out of fourteen. Source: NASA/ESA/CSA and STScI
This photo was taken with James Webb’s NIRcam instrument working in the near infrared between 0.6 and 5 micron wavelengths. In visible-light photographs, the planet appears as a blue dot due to its methane atmosphere. The infrared image allows us to observe a planet with a milky disk with bright spots and streaks on the surface corresponding to the methane ice clouds present in height on this icy planet. The south pole of the planet is surrounded by a vortex of high-altitude clouds.
In this shot, a line of light appears at the planet’s equator. According to astronomers, this is the hallmark of the atmospheric circulation that powers the winds and storms that take place on Neptune. Scientists know that Neptune is a planet with a capricious climate and the winds that blow on its surface can reach more than 1600 km/h!
The planet Neptune is surrounded by fourteen natural satellites, seven of which are clearly visible in the image. Proteus is clearly visible on the right of the image and is not hidden by Neptune’s rings. The other visible moons are Larissa, Despina, Thalassa, Naïade, Galatea, and Triton in the upper left corner, which looks like a star because it is so bright.
This image allows us to observe four of Neptune’s five rings with great precision. The outer ring was called Adams and the other three are Lassell, Le Verrier and Galle. The fifth called Arago, the closest to Neptune, is not visible.
(Also read: 3 discoveries about Neptune and its moons)
Neptune, the eighth planet of the solar system
In the solar system, the giant Saturn remains the planet whose rings are the most visible. However, she is not the only one who has it. James Webb just photographed Neptune’s rings, but planets like Uranus and Jupiter also have rings. However, they are difficult to see because they are very often made of ice dust that reflects little sunlight. Saturn’s rings reflect at least 60% of sunlight because they are made of large particles of water ice that can reach several meters in size.
The planet Neptune, which has just revealed its ring system through James Webb, is in a nearly circular orbit 4.5 billion kilometers from the Sun and takes 165 years to go around the Sun completely.
It is composed largely of helium and hydrogen, with the rest being water ice, ammonia, and methane that make up its mantle. Neptune also has a small rocky core. The planet’s atmosphere, which is 80% hydrogen and 19% helium, is 8,000 km thick and also contains trace amounts of methane which gives it its blue colour, as well as some ammonia, ethane and acetylene.
These unprecedented images of the planet Neptune show the incredible feats the James Webb Space Telescope is capable of. It allows not only to observe the deep space in the universe, but also the space closest to us within our solar system.
(Also read: What happens to the James Webb Telescope 1.5 million kilometers from Earth?)
“New Webb Image Captures Clearest View of Neptune’s Rings in Decades”, Webb Space TelescopeSeptember 21, 2022, https://webbtelescope.org/contents/news-releases/2022/news-2022-046