Using its near-infrared camera, the James Webb Space Telescope captured amazing images of Neptune and its rings. Thanks to the newly released images, we now see Neptune’s rings for the first time since 1989, when Voyager 2 performed the first flyby to the gas giant.

James Webb Space Telescope Neptune image
This infrared image from NASA’s James Webb Space Telescope shows Neptune, its rings, and its moons. The newly-released photos were taken using Webb’s near-infrared camera (NIRCam), which has three infrared filters that reveal details of planets that can’t be seen by the human eye. That’s why Neptune doesn’t appear as it normally does in the visible wavelength. Credit: NASA / ESA / CSA / STScI / Joseph DePasquale

James Webb’s image of Neptune and its moons

James Webb Space Telescope’s extremely stable and precise image quality permits these very faint rings so close to Neptune to be successfully detected.

Heidi Hammel, a Neptune system expert and interdisciplinary scientist for Webb, says:

“It has been three decades since we last saw these faint, dusty rings, and this is the first time we’ve seen them in the infrared.”

James Webb Space Telescope captured seven of Neptune’s 14 known moons: Galatea, Naiad, Thalassa, Despina, Proteus, Larissa, and Triton. The gas giant’s large and unusual moon, Triton, dominates this portrait of Neptune as a very bright point of light (at the upper-left) sporting the signature diffraction spikes seen in many of Webb’s images. Credits: NASA, ESA, CSA, STScI
Neptune and its satellites. James Web Space Telescope photo (annotated version)
Neptune and its moons Triton, Galatea, Naiad, Thalassa, Despina, Proteus, and Larissa. This is the annotated version of the photo above. Credits: NASA, ESA, CSA, STScI


Covered in a frozen sheen of condensed nitrogen, Triton reflects an average of 70 percent of the sunlight that hits it. In the images taken by the James Webb Space Telescope, Triton far outshines Neptune in the images 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 that was gravitationally captured by the gas giant.

Additional Webb studies of both Triton and Neptune are planned in the coming year.

Global Color Mosaic of Triton, taken by Voyager 2 in 1989
Global color mosaic of Triton, taken in 1989 by Voyager 2 during its flyby of the Neptune system. The color was synthesized by combining high-resolution images taken through orange, violet, and ultraviolet filters; these images were displayed as red, green, and blue images and combined to create this color version. Image source: NASA

With a radius of 1,350 km (839 mi), about 22% smaller than Earth’s moon, Triton is by far the largest satellite of Neptune. It is also one of the largest non-planets in our solar system (it is even larger than Pluto).

It is one of only three objects in the Solar System known to have a nitrogen-dominated atmosphere (the others are Earth and Saturn’s giant moon, Titan).

Triton has the coldest surface temperature in the Solar System

Triton has the coldest surface known anywhere in the Solar System (38 K, about -391 degrees Fahrenheit); it is so cold that most of Triton’s nitrogen is condensed as frost, making it the only satellite in the Solar System known to have a surface made mainly of nitrogen ice.

The pinkish deposits constitute a vast south polar cap believed to contain methane ice, which would have reacted under sunlight to form pink or red compounds. The dark streaks overlying these pink ices are believed to be icy and perhaps carbonaceous dust deposited from huge geyser-like plumes, some of which were found to be active during the Voyager 2 flyby.

The bluish-green band visible in this image extends all the way around Triton near the equator; it may consist of relatively fresh nitrogen frost deposits. The greenish areas include what is called the cantaloupe terrain, whose origin is unknown, and a set of “cryovolcanic” landscapes apparently produced by icy-cold liquids (now frozen) erupted from Triton’s interior.


M. Özgür Nevres
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