James Webb telescope captures detailed image of Neptune and its delicate, dusty rings

The James Webb Space Telescope has captured an image of a luminous Neptune and its delicate, dusty rings in detail not seen in decades, NASA said Wednesday. The last time astronomers had such a clear view of the farthest planet from the Sun was when NASA's Voyager 2 became the first and only space probe to fly past the ice giant for just a few hours in 1989.

Webb's unprecedented infrared imaging capabilities have helped provide a new glimpse into Neptune's atmosphere, said Mark McCaughrean, a senior advisor for science and exploration at the European Space Agency. The telescope "takes all that glare and background away" so that "we can start to tease out the atmospheric composition" of the planet, McCaughrean, who has worked on the Webb project for more than 20 years, told AFP.

In previous images taken by the Hubble Space Telescope, Neptune appears as deep blue due to methane in its atmosphere. However, the near-infrared wavelengths captured by Webb's primary imager NIRCam shows the planet as greyish white, with icy clouds streaking the surface.

"The rings are more reflective in the infrared," McCaughrean said, "so they're much easier to see".

You can also see an "intriguing brightness" near the top of Neptune, NASA said in a statement. Because the planet is tilted away from Earth and takes 164 years to orbit the Sun, astronomers have not yet had a good look at its north pole. 

Webb also spotted seven of Neptune's 14 known moons.

A zoomed-out image shows what appears to be a very bright spiky star, but is in fact Triton, Neptune's strange, huge moon haloed with Webb's famed diffraction spikes.

Triton is covered in ice, is larger than dwarf planet Pluto and appears brighter than Neptune. Neptune meanwhile "absorbs most of the light falling on it", McCaughrean said.

Because Triton orbits the wrong way around Neptune, it is believed to have once been an object from the nearby Kuiper belt which was captured in the planet's orbit. "So it's a pretty cool to go and have a look at," McCaughrean told AFP.