Dominating this Webb portrait of Neptune is a very bright point of light sporting the signature diffraction spikes seen in many of Webb’s images, but this is not a star. Webb also captured seven of Neptune’s 14 known moons. A previously-known vortex at the southern pole is evident in Webb’s view, but for the first time Webb has revealed a continuous band of high-latitude clouds surrounding it. Neptune’s 164-year orbit means its northern pole, at the top of this image, is just out of view for astronomers, but the Webb images hint at an intriguing brightness in that area. The atmosphere descends and warms at the equator, and thus glows at infrared wavelengths more than the surrounding, cooler gases. More subtly, a thin line of brightness circling the planet’s equator could be a visual signature of global atmospheric circulation that powers Neptune’s winds and storms. Keck Observatory, have recorded these rapidly evolving cloud features over the years. Images from other observatories, including the Hubble Space Telescope and the W.M. Such methane-ice clouds are prominent as bright streaks and spots, which reflect sunlight before it is absorbed by methane gas. In fact, the methane gas so strongly absorbs red and infrared light that the planet is quite dark at these near-infrared wavelengths, except where high-altitude clouds are present. Webb’s Near-Infrared Camera (NIRCam) images objects in the near-infrared range from 0.6 to 5 microns, so Neptune does not appear blue to Webb. This is readily apparent in Neptune’s signature blue appearance in Hubble Space Telescope images at visible wavelengths, caused by small amounts of gaseous methane. Compared to the gas giants, Jupiter and Saturn, Neptune is much richer in elements heavier than hydrogen and helium. This planet is characterized as an ice giant due to the chemical make-up of its interior. At that extreme distance, the Sun is so small and faint that high noon on Neptune is similar to a dim twilight on Earth. Located 30 times farther from the Sun than Earth, Neptune orbits in the remote, dark region of the outer solar system. Neptune has fascinated researchers since its discovery in 1846. Webb’s extremely stable and precise image quality permits these very faint rings to be detected so close to Neptune. “It has been three decades since we last saw those faint, dusty bands, 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. In addition to several bright, narrow rings, the Webb image clearly shows Neptune’s fainter dust bands. Most striking in Webb’s new image is the crisp view of the planet’s rings – some of which have not been detected since NASA’s Voyager 2 became the first spacecraft to observe Neptune during its flyby in 1989. Not only has Webb captured the clearest view of this distant planet’s rings in more than 30 years, but its cameras reveal the ice giant in a whole new light. NASA’s James Webb Space Telescope shows off its capabilities closer to home with its first image of Neptune.

Neptunes rings