Neptune with its distinct rings seen through James Webb Telescope

September 21, 2022

NASA’s James Webb Space Telescope has captured first images of Neptune and its moons as visible under the infrared spectrum. These remarkable images provide the clearest view of Neptune’s rings that have never been seen before in detail.

Webb’s Near-Infrared Camera (NIRCam) captures images in the near-infrared range from 0.6 to 5 microns, as a result Neptune does not appear blue to Webb. In fact, the methane gas so strongly absorbs red and infrared light that the planet is quite dark at these near-infrared wavelengths, except where high-altitude clouds are present. Such methane-ice clouds are prominent as bright streaks and spots, which reflect sunlight before it is absorbed by methane gas.

The size of Neptune is around four times that of Earth. For comparison, Neptune would be the size of a basketball if Earth were a huge apple. Neptune circles the Sun at a distance of around 2.8 billion miles and is the eighth planet from the Sun (4.5 billion kilometers). A Neptunian day on Neptune lasts for around 16 hours, and its orbit around the sun takes 165 Earth years (a Neptunian year). The ice giant Neptune. Over a tiny rocky core, a hot, dense fluid of "icy" substances including water, methane, and ammonia makes up the majority of its mass. Atomic helium, methane, and molecular hydrogen make up the majority of Neptune's atmosphere. There are 14 known moons of Neptune, and they all bear Greek mythological names for sea gods and nymphs. At least five of Neptune's primary rings and four other ring arcs are made of clusters of dust and debris that were probably created by the gravitational pull of a nearby moon.

These photos by Webb also include seven of the 14 known moons of Neptune. A very brilliant point of light with the distinctive diffraction spikes observed in many of Webb's photographs dominates this Webb painting of Neptune, however this object is not a star. This is Triton, the big and strange moon of Neptune. Triton reflects about 70% of the sunlight that it receives thanks to a frozen coating of condensed nitrogen covering it. Because methane absorbs at these near-infrared wavelengths, it outshines Neptune by a significant margin in this photograph. Triton's peculiar retrograde orbit around Neptune has led astronomers to hypothesize that this moon was once a Kuiper belt object that was gravitationally grabbed by Neptune. More Webb research on both Triton and Neptune are planned in the coming year.

Credit - NASA, ESA, CSA, and STScI ; Source: NASA