Webb's new images show Neptune's rings with a sharpness that hadn't been seen since 1989, when NASA's Voyager 2 flew past the planet for the first time.
After revealing stunning images of some of the most distant stars and galaxies and providing unprecedented views of Jupiter and Mars, the JWST continues studying our solar system. Neptune’s first image from NASA’s James Webb Space Telescope demonstrates the telescope’s capabilities when observing objects that are a bit closer to home. But this image of Neptune is special. It is not only Webb’s cameras that give a clear view of this distant planet’s rings for the first time in 30 years, but they also provide a new perspective on the ice giant itself.
Webb’s new images show Neptune’s rings with a sharpness that hadn’t been seen since 1989, when NASA’s Voyager 2 flew past the planet for the first time. Neptune’s fainter dust bands can also be seen in the Webb image, along with several bright, narrow rings. Heidi Hammel, an expert on the Neptune system and interdisciplinary scientist with Webb Space Telescope, notes that these faint, dusty rings have been seen before, but never in infrared. Webb’s extremely stable and precise image quality permits these very faint rings to be detected so close to Neptune.
Research into the planet Neptune dates back to its discovery in 1846. Neptune orbits in a dark, remote area of the outer solar system, 30 times farther from the Sun than Earth. On Neptune, high noon is like an earthly twilight due to how small and faint the Sun is. Considering the chemical composition of its interior, this planet is categorized as an ice giant. The abundance of elements heavier than hydrogen and helium on Neptune is much higher than that on Jupiter and Saturn, the gas giants. Neptune has a distinctive blue color caused by small amounts of gaseous methane that can be easily seen in Hubble Space Telescope images.
Neptune is not blue to Webb because its Near-Infrared Camera (NIRCam) images it in the near-infrared range from 0.6 to 5 microns. Due to its strong absorption of red and infrared light, methane causes the planet to appear quite dark at these near-infrared wavelengths, except where clouds are present at high altitudes. The bright streaks and spots that appear in such methane-ice clouds reflect sunlight before being absorbed by methane gas. These rapidly evolving cloud features have been captured over the years by other observatories, such as the Hubble Space Telescope and WM Keck Observatory.
Neptune’s winds and storms might be powered by global atmospheric circulation signaled by a thin line of brightness circling the planet’s equator. In the Ice giant’s equatorial region, the atmosphere warms and descends, causing it to glow brighter at infrared wavelengths than at other points.
Because of its 164-year orbit, Neptune’s northern pole can’t be seen by astronomers, but Webb’s images suggest a fascinating brightness there. The southern pole shows a previously-known vortex, but Webb shows a continuous band of high-latitude clouds surrounding it for the first time. Neptune has 14 known moons, seven of which were captured by Webb. An extremely bright point of light dominates Webb’s portrait of Neptune, bearing the diffraction spikes typical of its images, but it is not a star. Instead, this is Neptune’s unusually large moon Triton.
Condensed nitrogen covers the surface of Triton, allowing it to reflect an average of 70 percent of the sunlight it encounters. In this image, it is far more luminous than Neptune, whose atmosphere is dimmer due to methane absorption. Scientists speculate that Triton was originally a Kuiper belt object gravitationally captured by Neptune since it orbits in a backward (retrograde) orbit around Neptune. In the coming year, Webb will continue to study both Triton and Neptune.
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