The James Webb Space Telescope (JWST) has once again demonstrated its ability to capture not only distant galaxies, but also nearby objects – this time Neptune was in its lens. The ice giant appeared in a completely new light, and the image of its rings turned out to be the clearest in more than 30 years.
The most striking detail in the new image is indeed the planet’s rings, some of which have not been re-captured since 1989, when Voyager 2 flew past Neptune. Researchers’ interest in Neptune has not waned since its discovery in 1846. The planet revolves around the Sun at a distance of 30 times greater than the Earth – the star seems so small and dim that noon on Neptune is more like Earth’s twilight. Due to the chemical composition of the interior, the planet is characterized as an ice giant: unlike Jupiter and Saturn, there are many elements heavier than hydrogen and helium. This is clearly seen in the blue color of Neptune in the Hubble images taken in the visible range – the blue color is due to the presence of methane gas.
“James Webb” took pictures of the planet with a near-infrared camera (NIRCam) from 0.6 to 5 microns, so the planet does not appear blue in the latest images: methane gas absorbs red and infrared color well, so with the filters used, the planet appears dark except for areas with high altitude clouds. Clouds of methane ice show up as bright streaks and patches in the imagery—sunlight is partially reflected before being subsequently absorbed by the methane. A bright band along the planet’s equator may indicate the processes of global atmospheric circulation, generating powerful winds on Neptune. The north pole of the planet is still out of sight, but something bright is clearly visible in this area. The vortex already known to scientists in the region of the South Pole also got into the picture – for the first time, it was also possible to fix a continuous band of clouds located nearby.
The telescope photographed 7 of the 14 known satellites of Neptune. The brightest object in the image turned out to be a certain bright point, and this is not a star, but Neptune’s large and unusual satellite Triton. Because of the condensed nitrogen, it reflects about 70% of the sunlight falling on it, and in the infrared it clearly appears brighter than the planet itself, where the radiation is absorbed by methane. In addition, Triton revolves around Neptune in an unusual retrograde orbit, opposite to the direction of movement of other satellites. Astronomers suggest that it originally belonged to the Kuiper belt, but was subsequently captured by the planet. Additional studies of both objects are scheduled for next year.
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