As if delightful iridescent fairies were racing on a cosmic track, Neptune’s rings sparkle in a stunning new view captured by the James Webb Space Telescope (JWST), the most powerful extraterrestrial observatory ever built. This is the sharpest image of the planet’s rings obtained from flying over Voyager 2 in 1989 and reveals a myriad of details never seen before.
“For me, looking at JWST’s new image of Neptune is like finding a friend you haven’t seen in over ten years, and they look GREAT,” Jane Rigby, an astrophysicist at NASA’s Goddard Space Flight Center who serves as JWST operational project, he says in an email.
After a breathtaking launch on Christmas Day 2021, the telescope began operating at full capacity this July and has since made headlines with jaw-dropping images of nebulae and discoveries of ancient galaxies that could “break cosmology.” But JWST’s keen infrared eyes are opening new perspectives even closer to home when they turn to the aftermath of the worlds of our solar system.
For example, the telescope view of Neptune shows the planet’s faint dust bands with unprecedented clarity. These show up as blurry particles among the brightest, ice-dominated rings, says Mark McCaughrean, senior science advisor at the European Space Agency (ESA) and a member of the JWST Science Working Group.
When University of Arizona astronomer Marcia Rieke had a chance to observe the new views of Neptune, she says, “As usual, I am amazed at what we see.” Rieke, who is currently the principal investigator of JWST’s principal imager, called the Near Infrared Camera (NIRCam), remembers attempting to observe Neptune’s rings years ago using a ground-based telescope on Kitt Peak in Arizona. “We haven’t seen practically anything due to how thin and clunky the rings are,” she says. “It is wonderful to see them so clearly and easily [with JWST]. “
Methane ice clouds appear as streaks and bright spots in the image, glowing in the faint sunlight that reaches Neptune from about 2.8 billion miles away. Seven of the planet’s 14 moons are also hidden in JWST’s photograph. The brightest is the strange Triton, a powerful natural satellite covered in nitrogen ice that reflects about 70 percent of the incoming sunlight. While most planetary moons, including all others around Neptune, orbit with the rotation of their planetary host, Triton does so in the opposite direction. That orbit suggests to researchers that the body is likely a migrant from the outer solar system captured long ago by Neptune’s gravity.
“It will be really nice to measure the spectrum of Triton because it represents a body that comes from further away,” says McCaughrean.
JWST’s infrared view also shows a thin band of light surrounding the equator, likely produced by hotter gas flowing towards Neptune’s mid-latitudes as part of an ever-changing pattern of global atmospheric circulation. Such features could drive the planet’s powerful winds and storms, according to an ESA press release.
“What really comes to mind are all the wonderful clouds and storms that are present in Neptune’s atmosphere,” says Nikole Lewis, associate professor of astronomy at Cornell University. “Neptune has the highest wind speeds measured in the solar system, with average wind speeds close to it [the] at the equator of 700 mph and peak wind speeds in locations exceeding 1,000 mph. While Lewis’s work with JWST will focus on planets beyond the solar system, he calls the new image “an incredible snapshot of its turbulent climate.”
Unlike Voyager 2, which has provided snapshots of Neptune from a moment in time, JWST’s studies of Neptune and other inhabitants of the solar system will continue as long as the observatory itself lasts. By comparing these and future JWST images to those of Voyager 2, scientists hope to learn more about long-term atmospheric changes on the planet, such as the seasons of Neptune, McCaughrean says. Since the planet is tilted at an angle of 28 degrees along its axis, it experiences four seasons, just like the Earth. But on Neptune, each lasts about 40 years as a result of that world’s 164 Earth-year long journey around the sun. That means the planet has almost entered a different season since it flew via Voyager 2, McCaughrean says.
Although Neptune may be the crown jewel of the newly released snapshot, the zoomed-in view shows “some of the poetic side of planets suspended in space,” says McCaughrean, referring to the backdrop of distant stars and galaxies that appear to surround the ice giant. .
Nearly a million miles from Earth and chock full of imaging tools, JWST will continue to provide deeper and clearer insights into the universe and our place in it. “JWST, even in just a couple of months, has already started adding that cosmic perspective,” says McCaughrean. “But to be honest, you haven’t seen anything yet.”