Since its discovery in 1846, the planet Neptune has been the topic of fascination for scientists. Neptune orbits in the remote, dark region of the outer solar system. The planet is also an ice giant because of its internal chemical composition.
Its been three decades since scientists have observed Neptune rings. Now, NASA’s James Webb Space Telescope shows off its capabilities closer to home with its first image of Neptune. The Webb telescope has captured Neptune’s rings.
This is the first time scientists have seen them in infrared. 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.
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. The methane gas absorbs red and infrared light so strongly that the planet is quite dark at these near-infrared wavelengths, except where high-altitude clouds are present.
Heidi Hammel, a Neptune system expert and interdisciplinary scientist for Webb, said, “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. The methane gas absorbs red and infrared light so strongly that the planet is quite dark at these near-infrared wavelengths, except where high-altitude clouds are present. 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 W.M. Keck Observatory, have recorded these rapidly evolving cloud features over the years.”
“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. The atmosphere descends and warms at the equator, and thus glows at infrared wavelengths more than the surrounding, cooler gases.”
Neptune’s northern pole, near the top of this image, is just out of sight for astronomers due to its 164-year orbit, but the Webb images suggest an unusual brightness there. Webb’s image clearly shows a previously known vortex around the southern pole, but this is the first time Webb has shown a continuous band of high-latitude clouds surrounding it.
Seven of the 14 known moons of Neptune were also captured by Webb. A very bright point of light with the distinctive diffraction spikes observed in many of Webb’s photographs dominates this Webb painting of Neptune, however, this object is not a star. This is Triton, the big and strange moon of Neptune.
NASA’S official said, “Covered in a frozen sheen of condensed nitrogen, Triton reflects an average of 70 percent of the sunlight that hits it. It far outshines Neptune in this image because the planet’s atmosphere is darkened 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 gravitationally captured by Neptune. Additional Webb studies of both Triton and Neptune are planned in the coming year.”