The newly deployed James Webb Space Telescope has captured the clearest view of Neptune in decades.
The most powerful space telescope ever built, which launched at the end of 2021, used its infrared imaging capabilities to show the distant planet in a fresh light. Features include Neptune’s prominent narrow rings and fainter dust bands, which NASA says have not been detected since 1989 when Voyager 2 passed close by.
“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,” Heidi Hammel, a Neptune system expert and interdisciplinary scientist for Webb, said on NASA’s website.
Neptune is located in the outer solar system, 30 times further from the sun than Earth, and was discovered by astronomers in 1846. NASA says that Neptune’s vast distance from our sun means that high noon on the planet is “similar to a dim twilight on Earth.”
The planet’s usual blue appearance, in images captured by Voyager and the Hubble Space Telescope, is the result of the absorption of red and infrared light by Neptune’s methane atmosphere. But Webb’s Near-Infrared Camera (NIRCam) captures objects in the near-infrared range from 0.6 to 5 microns, so Neptune does not appear blue to Webb.
The image taken by the Webb telescope also shows seven of Neptune’s 14 known moons, including its largest, Triton. You can see them in the image below.
“Covered in a frozen sheen of condensed nitrogen, Triton reflects an average of 70% of the sunlight that hits it,” NASA says of its bright appearance. “It far outshines Neptune in this image because the planet’s atmosphere is darkened by methane absorption at these near-infrared wavelengths.”
The space agency notes that Triton orbits Neptune in an unusual backward (retrograde) orbit, behavior that suggests it could once have been part of the Kuiper Belt — a band of rock, ice, comets, and dwarf planets in the outer solar system — before being gravitationally captured by Neptune.
The Webb team plans to use the space telescope to conduct further studies of Neptune in the coming year.
The Webb mission is the work of NASA, the European Space Agency, and the Canadian Space Agency, and launched in December 2021. The telescope is being used mainly to explore the depths of the universe for clues on how it all began, while at the same time searching for planets similar to our own that could support life. The team is also taking the opportunity to use the telescope’s powerful technology to image familiar planets closer to home, such as Neptune and Jupiter, showing them in ways that we’ve never seen them before.