James Webb captures never-before-seen images of Neptune

James Webb captures never-before-seen images of Neptune

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It’s been more than 30 years since Neptune’s rings have appeared so clearly. The James Webb Telescope has just produced impressive new images of this ice giant located at the edge of our solar system. We can distinguish not only four of its rings, including the thinnest, but also seven of its 14 natural satellites, notably Triton, which appears even brighter than its planet.

The last detailed images of Neptune’s rings come from 1989, when NASA’s Voyager 2 probe flew past the outermost planet in the Solar System. Located about 30 AU from the Sun, Neptune is the densest giant planet in our system; Due to its internal composition – a shell composed of water ice, ammonia and methane, at the top of which is an atmosphere of helium, hydrogen and methane – it is classified as an ice giant. It is given its characteristic blue color at wavelengths in the visible spectrum by methane gas.

With James Webb’s near- and mid-infrared telescope, Neptune doesn’t appear blue: methane absorbs red and infrared light so strongly that the planet appears rather whitish, except where high-altitude ice clouds sit that reflect sunlight before. it is absorbed by the gas (hence the bright spots we see on the planet). The telescope eliminates glare from reflected sunlight and offers a completely new view of the planet.

Valuable information about Neptune’s atmosphere

In this image, we can clearly distinguish two bright rings of Neptune – including the Adams ring, the outermost from the planet – as well as two fainter rings. They’re all made of dust, which makes them particularly difficult to spot (by comparison, Saturn’s rings are made mostly of ice chunks, so they look much brighter). ” It’s been three decades since we saw these fine, dusty rings, and this is the first time we’ve seen them in infrared light. », points out Heidi HammelNeptune System Specialist and Interdisciplinary Scientist for Webb.

Neptune seen at different wavelengths, Hubble (left) and James Webb (right). © Twitter/NASAHubble

This new image also provides valuable insights into Neptune’s atmosphere. Indeed, we can make out a fine line of light encircling the planet’s equator, which could be a visual signature of the atmospheric circulation fueling Neptune’s extremely fast winds and storms: the atmosphere descends and warms at the equator, so it shines brighter. at infrared wavelengths than the cooler surrounding gases, NASA explains.

The north pole of the planet is out of sight for astronomers, but an interesting luminosity can be seen in this area. At the level of the South Pole, HST has already enabled highlighting several dark eddies, swirling atmospheric systems under high pressure, disappear within a few years and usually accompanied by bright clouds. The image captured by Webb confirms the presence of the vortex, but for the first time revealed the presence of a continuous band of high-latitude clouds around it.

Further observations of the Neptunian system pending

Neptune has 14 known moons. The largest of these, Triton, was discovered in 1846. It appears on the top of the planet in the image, very bright and has the now famous eight diffraction peaks thanks to the telescope’s mirrors.

Moon Neptune James Webb
James Webb imaged Neptune, its rings and seven of its moons. © NASA/ESA/CSA/STScI

Triton is the only known large satellite of the solar system to orbit in a retrograde direction, i.e. against the direction of rotation of its planet. Its surface is composed mostly of nitrogen ice, and the Moon reflects an average of 70% of the sunlight it receives. Triton also has an atmosphere composed mostly of nitrogen (which is why it appears brighter here than its planet). Because of its unusual orbit, astronomers believe that this moon was originally a Kuiper Belt object that was gravitationally captured by Neptune.

Six other moons appear in the image: Naiad, Thalassa, Despina, Galatea, Larissa and Proteus. Neptune’s moon system is particularly strange and diverse; therefore, further observations of Neptune and Triton are planned next year.

This new view of Neptune will undoubtedly make it easier to find and observe exoplanets in our galaxy. Indeed, astronomers have found that those of the genus Neptune or Uranus are the most common.

source: NASA

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