New Webb image captures the brightest view of Neptune’s rings in decades

What do we see in Webb’s latest image of the ice giant Neptune? Webb captured seven of Neptune’s 14 known moons: Galatea, Naiad, Thalassa, Despina, Proteus, Larissa, and Triton. Neptune’s large and unusual moon, Triton, dominates this Webb portrait of Neptune as a very bright point of light with the distinctive diffraction peaks seen in many of Webb’s images. Credit: NASA, ESA, CSA, STScI

NASA’s James Webb Space Telescope shows its capabilities closer to home with its first image of Neptune. Not only has Webb captured the clearest view of this distant planet’s rings in more than 30 years, but his cameras reveal the ice giant in a whole new light.

Most notable in Webb’s new image is the sharp image of the planet’s rings — some of which have not been detected since NASA’s Voyager 2 became the first spacecraft to observe Neptune in flight in 1989. In addition to several bright, narrow rings, the Webb has image clearly shows Neptune’s fainter dust bands.

“It’s been three decades since we last saw these faint, dusty rings, and this is the first time we’ve seen them in infrared,” said Heidi Hammel, a Neptune systems expert and interdisciplinary scientist for Webb. Thanks to Webb’s extremely stable and accurate image quality, these very faint rings can be detected so close to Neptune.

Neptune has fascinated researchers since its discovery in 1846. Neptune is located 30 times farther from the sun than Earth and orbits in the remote, dark region of the outer solar system. At that extreme distance, the sun is so small and dim that noon on Neptune is comparable to a twilight twilight on Earth.

This planet is characterized as an ice giant due to the chemical composition of its interior. Compared to the gas giants Jupiter and Saturn, Neptune is much richer in elements heavier than hydrogen and helium. This can be clearly seen in Neptune’s distinctive blue appearance in Hubble Space Telescope images at visible wavelengths, caused by small amounts of gaseous methane.

New Webb image captures the brightest view of Neptune's rings in decades

Credit: NASA, ESA, CSA, STScI

Webb’s Near-Infrared Camera (NIRCam) images objects in the near-infrared range of 0.6 to 5 microns, so Neptune doesn’t appear blue to Webb. In fact, the methane gas absorbs red and infrared light so strongly that the planet is quite dark at these near-infrared wavelengths, except where there are high-altitude clouds. Such methane ice clouds are prominent as bright streaks and spots, which reflect sunlight before it is absorbed by methane gas. Images from other observatories, including the Hubble Space Telescope and the WM Keck Observatory, have captured these rapidly evolving cloud features over the years.

More subtly, a thin line of brightness encircling the planet’s equator could be a visual signature of the global atmospheric circulation that drives Neptune’s winds and storms. The atmosphere descends and warms at the equator, thus glowing more at infrared wavelengths than the surrounding, cooler gases.

Neptune’s 164-year orbit means that the north pole, at the top of this image, is just out of view for astronomers, but the Webb images indicate an intriguing brightness in that area. A previously known vortex at the South Pole is clearly in Webb’s view, but for the first time, Webb has revealed a continuous band of high-latitude clouds around it.

Webb also captured seven of Neptune’s 14 known moons. This Webb portrait of Neptune dominates a very bright point of light with the distinctive diffraction peaks seen in many of Webb’s images, but this is not a star. Rather, this is Neptune’s large and unusual moon, Triton.

Covered in a frozen glow of condensed nitrogen, Triton reflects an average of 70% of the sunlight that hits it. It far outshines Neptune in this image, as the planet’s atmosphere is obscured by methane absorption at these near-infrared wavelengths. Triton orbits Neptune in an unusual backward (retrograde) orbit, leading astronomers to speculate that this moon was originally a Kuiper Belt object captured by Neptune’s gravity. Additional Webb studies of both Triton and Neptune are planned in the coming year.


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Provided by NASA’s Goddard Space Flight Center

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