Neptune and its Rings Shown in a Striking New Light by the Webb Telescope | Astronomy


The James Webb Space Telescope has turned its gaze from the deep universe to our home solar system, capturing an image of bright Neptune and its delicate, dusty rings in detail not seen in decades.

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 by the icy giant for just a few hours in 1989.

Now, Webb’s unprecedented infrared imaging capability has provided new insight into Neptune’s atmosphere, said Mark McCaughrean, senior advisor for science and exploration at the European Space Agency.

The telescope “removes all that glare and background” so that “we can start to sort out the atmospheric makeup” of the planet, said McCaughrean, who has worked on the Webb project for more than 20 years.

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

Side-by-side photos of Neptune taken by Voyager 2 in 1989, Hubble in 2021, and Webb in 2022. Photography: AP

However, near-infrared wavelengths captured by Webb’s main NIRCam imager show the planet a greyish-white, with icy clouds streaking the surface.

“Rings are more reflective in the infrared,” McCaughrean said, “so they’re much easier to see.”

The image also shows “intriguing brightness” near Neptune’s top, NASA said in a statement. Because the planet is tilted relative to Earth and takes 164 years to orbit the sun, astronomers have yet to get a good look at its north pole.

Webb also spotted seven of Neptune’s 14 known moons. Overlooking Neptune in a magnified image is what appears to be a very bright spiky star, but it’s actually Triton, Neptune’s strange, huge moon haloed with Webb’s famous diffraction spikes.

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

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

Because Triton orbits Neptune the wrong way, it is believed to have once been a nearby Kuiper Belt object that was captured in the planet’s orbit. “So it’s pretty cool to go in there and take a look,” McCaughrean said.

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

Operational since July, Webb is the most powerful space telescope ever built and has already released many unprecedented data. Scientists hope this will herald a new era of discovery.

Research based on Webb’s observations of Neptune and Triton is expected next year.

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

“Of course we knew it would do this, we built it to do this, it’s exactly the machine we designed. But suddenly starting to see things in these longer wavelengths, which was impossible before…it’s just remarkable.


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