Webb's latest picture is startling because it clearly shows the planet's rings, some of which have not been seen since NASA's Voyager 2 .
With its first picture of Neptune, NASA's James Webb Space Telescope displays its capabilities on a far more familiar scale. Webb's cameras shed fresh light on the gas giant, and they also obtained the sharpest glimpse of the planet's rings in more than 30 years.
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Webb's latest picture 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 bands are also visible in the Webb picture, along with many brilliant, thin rings.
“It has 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 Hammel, a Neptune system expert and interdisciplinary scientist for Webb. These very faint rings can be observed so near to Neptune because of Webb's exceptionally consistent and accurate picture quality.
Scientists have been captivated with Neptune ever since it was discovered in 1846. Neptune orbits in the distant, dark area of the outer solar system, at a distance 30 times that of Earth from the Sun. Due to the Sun's tiny size and low brightness at such a great distance, the middle of the day 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 colour due to trace concentrations of gaseous methane.
Since the near-infrared range of Webb's Near-Infrared Camera (NIRCam) is between 0.6 and 5 microns, Neptune does not seem blue to Webb. In reality, the planet is fairly black at these near-infrared wavelengths, especially in regions where high-altitude clouds are prevalent, since the methane gas absorbs this light so powerfully. Clouds composed of methane ice are easily recognisable as brilliant streaks and patches because they reflect sunlight before the gas absorbs it. These quickly changing cloud structures have been captured throughout the years by the Hubble Space Telescope and the W.M. Keck Observatory, among other observatories.
Seven of Neptune's fourteen moons were also photographed by Webb. In this painting of Neptune by Webb, the brightest feature is not a star but rather Webb's distinctive diffraction spikes, which can be seen in many of his photographs. This is really Triton, Neptune's massive and peculiar moon.
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 "Photo: NASA")
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