Webb sees Neptune’s rings and moons
The new Webb telescope in space has been looking closer at home lately. It has moved into our solar system from its images of the most distant known galaxies. It has already set its sights on Mars and Jupiter. And now we are enjoying these new views of our solar system’s outermost major planet, Neptune. NASA released these images today (September 21, 2022) — our clearest view of Neptune in more than 30 years. We haven’t seen Neptune, its family of moons, and its two bright rings and faint dust bands in such detail since Voyager 2’s flyby in 1989.
Why Webb Can’t See Blue Neptune
Neptune orbits the sun about 30 times farther than Earth. It is the most distant and smallest of the four gas giant planets in the outer solar system. It looks blue to the eye through a small telescope. And its beautiful blue appearance was captured by Hubble in visible light.
Neptune’s deep gaseous atmosphere consists mostly of hydrogen and helium. The blue color is a sign that its atmosphere contains more methane than either Jupiter or Saturn. But in Webb’s near-infrared images, the familiar blue color disappears. That’s because methane gas is a strong absorber of red and infrared light.
Where’s the methane? It’s still there, and Webb’s near-infrared (NIRCam) camera is picking it up in Neptune’s high clouds. In Webb’s images, the prominent methane ice plumes may appear as bright streaks and dots. We can see them because they reflect sunlight before Methane gas has the ability to absorb the infrared light.
See more in Webb’s pictures
The new Webb images also show Neptune’s south pole, including a vortex with the high-latitude clouds surrounding it. The North Pole is out of our view, but there is an intriguing bright glow towards this region.
And maybe you can see the thin line around the planet’s equator. This is not part of Neptune’s ring system. In these Webb images, the rings cross above and below and behind the planet. Instead, this line around Neptune’s equator could be a sign of the global atmospheric circulation driving Neptune’s winds and storms. At the equator, the atmosphere sinks and warms, glowing more in the infrared than the surrounding areas.
cool what? Weather observation on another world …
Neptune’s rings in all their glory
Neptune’s rings are far too faint to be seen with small telescopes. Large terrestrial telescopes first saw them as “bows” in 1984. But it took the passage of the Voyager spacecraft in 1989 to see them clearly. In these new Webb images you can see Neptune’s outer ring – called the Adam ring – for John Couch Adams, whose precision mathematics led to the discovery of Neptune in 1846. On the left there is a bright moon, Galatea. Galatea lies right in the ring and acts as a shepherd for him.
Moving inward, the weak layer of material that comes next forms the Lassell and Arago rings. The next glowing ring is Le Verrier. On the right side of the image, the bright moon Despina lies directly within and is the shepherd for the Le Verrier ring.
Finally, the fainter ring closest to the planet is called the Galle ring.
All of these names are of course terrestrial names applied to Neptune and made official by the International Astronomical Union among terrestrial astronomers.
Heidi Hammel, an interdisciplinary scientist at the James Webb Telescope Project, said:
It’s been three decades since we last saw these faint, dusty rings. And this is the first time we’ve seen them in the infrared.
Neptune’s big moon Triton
Webb has captured seven of Neptune’s 14 known moons. Triton, Neptune’s largest moon, looks almost like a star with its bright diffraction peaks in the new Webb images.
Triton is an unusual satellite. It’s covered in frozen nitrogen, which makes it so reflective. She reflects 70% of the sunlight that hits her back into space. Triton also orbits Neptune in a retrograde orbit. Scientists believe that before it was a moon, it was a Kuiper Belt object that wandered too close to Neptune’s gravitational well.
Wide field view of Neptune
Webb plans to study Neptune and Triton again next year. In the meantime, let’s enjoy this wide-angle view of the 8th planet, its rings and strange moon floating in the depths of our solar system, while more distant galaxies glow in the background.
Conclusion: Webb sees Neptune’s rings and moons! They are the best images in 30 years since Voyager 2 swept by. Check out the new Webb images here.