With his first picture of Neptune, NASA’s James Webb Space Telescope shows its capabilities on a much more familiar scale. Webb’s cameras shed new light on the gas giant and also obtained the sharpest view of the planet’s rings in more than 30 years.
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Hey Neptune. did you ring
Webb’s latest image is the clearest look at Neptune’s rings in 30+ years, and the first time we’ve seen them in infrared light. Enjoy Webb’s ghostly, ethereal views of the planet and its dust lanes, rings and moons: #IAC2022 pic.twitter.com/17QNXj23ow— NASA Webb Telescope (@NASAWebb) September 21, 2022
Webb’s latest image is startling because it clearly shows the planet’s rings, some of which have not been seen since NASA’s Voyager 2 made the first close flyby of Neptune in 1989. Neptune’s fainter dust lanes are also visible in Webb’s image. along with many shiny, thin rings.
“It’s been three decades since we last saw these faint, dusty rings, and this is the first time we’ve seen them in the infrared,” notes Heidi Hamel, a Neptune system expert and interdisciplinary scientist for Webb. These very faint rings can be seen so close to Neptune because of the extremely consistent and accurate quality of Webb’s picture.
Scientists have been captivated by Neptune since it was discovered in 1846. Neptune orbits in the far, dark region of the outer solar system, 30 times Earth’s distance from the Sun. Because of the Sun’s small size and low brightness at such a great distance, midday on Neptune is roughly equivalent to the early hours of dawn on Earth.
In terms of its chemical composition, this planet is classified as an ice giant. Neptune, unlike Jupiter and Saturn, has a relatively high abundance of elements other than hydrogen and helium. Images of Neptune taken by the Hubble Space Telescope at visible wavelengths reveal that the planet has its characteristic blue color due to trace concentrations of methane gas.
Because the near-infrared range of Webb’s Near Infrared Camera (NIRCam) is between 0.6 and 5 microns, Neptune does not appear blue to Webb. In reality, the planet is relatively black at these near-infrared wavelengths, especially in high-altitude cloud-dominated regions, because the methane gas absorbs this light so strongly. Clouds composed of methane ice are easily recognizable as bright streaks and spots because they reflect sunlight before the gas absorbs it. These rapidly changing cloud structures have been imaged over the years by the Hubble Space Telescope and the WM Keck Observatory, among other observatories.
Seven of Neptune’s fourteen moons were also photographed by Webb. In this picture of Webb’s Neptune, the brightest feature is not a star, but rather Webb’s distinctive diffraction spikes, which can be seen in many of his pictures. This is indeed Triton, Neptune’s massive and peculiar moon.