Since the first release of its full-color images and spectroscopic data on July 12, 2022, NASA’s $10 billion James Webb Space Telescope set its sights on distant stars, nebulae and colorful galaxies far afield. On Wednesday, it provided a clearer look at a celestial body with which many are familiar but some might not readily recognize.
NASA noted that this is the clearest view of Neptune’s rings since the spacecraft Voyager 2 flew 3,408 miles above the planet’s north pole 33 years ago. It also provides a good look at the planet’s fainter dust bands.
Whereas previous images have depicted Neptune as blue, Webb’s Near-Infrared Camera (NIRCam) captures images of objects in the near-infrared range from 0.6 to 5 microns. Since the methane gas in the planet’s atmosphere absorbs red and infrared light, NASA reported the light appears dark with the exception to those spots where high-altitude clouds are present.
The NIRCam is capable of detecting light from the earliest stars and galaxies in the process of formation as well as the population of stars in nearby galaxies.
Heidi Hammel, a Neptune system expert and interdisciplinary scientist for Webb, noted, “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.”
Some of these rings have been named. In order from those nearest the planet then proceeding outward, they are: Galle, Leverrier, Lassell, Arago, and Adams.
In addition to dusty bands and rings, Webb’s image captured the planet’s 14 known moons: Galatea, Naiad, Thalassa, Despina, Proteus, Larissa, and Triton.
In the zoomed-out image (below), Triton appears to be a spiky star. Triton, which is bigger than Pluto, appears brighter because it is covered in ice and the ice reflects light.
At the top of the image, just out of view, is the planet’s north pole. Its south pole, clearly visible, has about its vortex a continuous band of high-altitude clouds.
Discovery and properties
Neptune, the eighth planet, was discovered in 1846. Although imperceptible to the naked eye, astronomers were able to track down the ice giant with a telescope, guided by mathematic calculations related to observed disruptions in the orbit of Uranus.
Although several astronomers had previously observed Neptune, they had not recognized it to be a planet. Johann Gottfried Galle was the first to observe the new planet with the Fraunhofer telescope at the Berlin Observatory on September 23, 1846. He had utilized Urbain Jean-Joseph Le Verrier’s calculations, who like John Couch Adams in England, had calculated the position of the planet.
Per Verrier’s suggestion, the planet was named after the mythological Roman god of the sea.
Neptune is roughly four times wider than Earth. To illustrate the difference, NASA likened Earth to a nickel (not to say it is flat), and Neptune to a baseball.
It takes Neptune 165 Earth years to complete its orbit around the sun, and completes its rotation every 16 hours.
Of the giant planets, Neptune is the densest. It has a relatively small rocky core, lacks a solid surface, and is 80% comprised of a hot, dense slurry of water, methane, and ammonia. Its atmosphere is majoritively comprised of molecular hydrogen, atomic helium and methane.
Other Webb captures
Earlier this month, NASA released images taken by the Webb of the Tarantula Nebula star-forming region. The Tarantula Nebula resides 161,000 light-years away in the Large Magellanic Cloud galaxy.
In August, the Phantom Galaxy, M74, was shown in infrared. This spiral galaxy is 32 million light-years away in the constellation Pisces. According to NASA, it lies almost face-on to Earth.
Images of Jupiter in infrared, highlighting its “Great Red Spot” were also shared in August.
“Cosmic Cliffs” was among the first images taken by Webb to be shared in July. This image highlights the edge of a gaseous cavity with a star-forming region called NGC 3324 in the Carina Nebula.