The James Webb Space Telescope has turned its gaze from the depths of the universe to our own solar system, capturing images of glowing Neptune and its delicate dust rings in detail not seen in decades.

The last time astronomers had such a clear view of the sun’s farthest planet was when NASA’s Voyager 2 became the first and only spacecraft to fly past the ice giant for just a few hours in 1989.

Now, Webb’s unprecedented infrared capabilities have provided a new look into Neptune’s atmosphere, said Mark McCorrin, senior adviser for science and research at the European Space Agency.

The telescope “takes away all that glare and background” so “we can start to tease out the composition of the atmosphere” of the planet, said McCaughrin, who has worked on the Webb project for more than 20 years.

In previous images taken by the Hubble Space Telescope, Neptune appears deep blue due to the methane in its atmosphere.

Close-up photos of Neptune taken by Voyager 2 in 1989, Hubble in 2021, and Webb in 2022. Photo: AP

However, near-infrared wavelengths captured by Webb’s primary NIRCam image show the planet grayish-white with icy clouds streaking the surface.

“The rings are more reflective in the infrared,” McCaughrin said, “so they’re much easier to see.”

The image also shows 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. Overhanging Neptune in the zoomed-in image is what looks like a very bright spiny star, but is actually Triton, Neptune’s strange, huge moon, covered in a halo of Webb’s famous diffraction spikes.

Neptune and seven of its 14 known moons, including Triton (top left).
Neptune and seven of its 14 known moons, including Triton (top left). Photo: Space Telescope Science Institute/ESA/Webb/AFP/Getty Images

Triton, which is larger than dwarf planet Pluto, appears brighter than Neptune because it is covered in light-reflecting ice. Meanwhile, Neptune “absorbs most of the light that falls on it,” McCaughrin said.

Because Triton orbits Neptune in the wrong direction, it is believed to have once been an object from the nearby Kuiper Belt that was captured in the planet’s orbit. “So to go and see it is pretty cool,” McCaughrin said.

As astronomers scour the universe for other planets like ours, they’ve discovered that ice giants like Neptune and Uranus are the most common in the Milky Way. “By being able to look at these giants in detail, we can use our observations of other ice giants,” McCaughrin said.

The Webb Telescope, which has been operating since July, is the most powerful space telescope ever built, and it has already released an unprecedented amount of data. Scientists hope it heralds a new era of discovery.

Studies based on Webb’s observations of Neptune and Triton are expected next year.

“The kind of astronomy we see now was unimaginable five years ago,” McCaughrin said.

“Of course we knew it could do it, we built it for it, it’s exactly the car we designed. But to suddenly start seeing things in these longer wavelengths that weren’t possible before … it’s just amazing.”

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