NASA’s James Webb Space Telescope shows off its capabilities near home with its first image of Neptune. Not only has Webb captured the clearest view of this distant planet’s rings in more than 30 years, but his cameras are revealing the ice giant in a whole new light.
Most noticeable in Webb’s new image is the clear view of the planet’s rings — some of which have not been discovered since NASA’s Voyager 2 became the first spacecraft to observe Neptune in flight in 1989. In addition to the many bright and narrow rings, Webb clearly shows the image. Faint dust bands of Neptune.
“It’s been three decades since we last saw these faint, dusty rings, and this is the first time we’ve seen them in infrared,” notes Heidi Hamill, a Neptune system expert and Webb interdisciplinary scientist. The fine and accurate image quality allows Webb to detect these very faint rings near Neptune.
Neptune has fascinated researchers since its discovery in 1846. Neptune is 30 times farther from the sun than Earth, and Neptune orbits in the remote, dark region of the outer solar system. At that extreme distance, the Sun is so small and faint that Neptune’s appearance resembles a faint twilight on Earth.
This planet is characterized as an ice giant due to the chemical composition of its interior. Compared to the gas giants, Jupiter and Saturn, Neptune is much richer in elements heavier than hydrogen and helium. This is easily illustrated by the distinctive blue appearance of Neptune in the Hubble Space Telescope images at Visible wavelengthsdue to small amounts of methane.
The Web’s Near Infrared Camera (NIRCam) images objects in the near-infrared range from 0.6 to 5 microns, so Neptune does not appear in Webb’s blue. In fact, red methane is strongly absorbed by infrared light That the planet is completely dark at these near-infrared wavelengths, except for places where clouds are located at high altitudes. Icy methane clouds appear as bright streaks and spots that reflect sunlight before it is absorbed by the methane gas. Images from other observatories, including the Hubble Space Telescope and the WM Keck Observatory, have recorded these rapidly evolving cloud features over the years.
More precisely, a thin line of brightness circling the planet’s equator could be a visual sign of the global atmospheric circulation that feeds Neptune’s winds and storms. The atmosphere lowers and warms at the equator, and thus glows at infrared wavelengths more than the cooler surrounding gases.
Neptune’s 164-year orbit means that the North Pole, at the top of this image, is out of astronomers’ view, but Webb’s images indicate an interesting brightness in that region. The previously known vortex appears at the South Pole from Webb’s view, but for the first time Webb has revealed a continuous collection of clouds at the high latitudes surrounding it.
Webb also captured seven of Neptune’s fourteen known moons. Dominating this Webb image of Neptune is a very bright spot of light characterized by the characteristic diffraction spikes seen in many of Webb’s images, but this is not a star. Instead, this is Neptune’s large and unusual moon, Triton.
Covered in a frigid sheen of condensed nitrogen, Triton reflects an average of 70% of the sunlight that strikes it. It greatly outperforms Neptune in this image because the planet’s atmosphere darkens by absorbing methane at near-infrared wavelengths. Triton orbits Neptune in an unusual retrograde (retrograde) orbit, leading astronomers to speculate that this moon was originally a Kuiper Belt object that was gravitationally captured by Neptune. Additional web studies for Triton and Neptune are scheduled for next year.
NASA’s Goddard Space Flight Center
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