![]() The radiation belts will have a complex structure owing to the absorption of energetic particles by the moons and rings of Neptune and losses associated with the significant changes in the diurnally varying magnetosphere configuration. The rings and all the known moons of Neptune are imbedded deep inside the magnetosphere, except for Nereid, which is outside when sunward of the planet. The auroral zones are most likely located far from the rotation poles and may have a complicated geometry. As the spacecraft exited the magnetosphere, the magnetic tail appeared to be monopolar, and no crossings of an imbedded magnetic field reversal or plasma neutral sheet were observed. The obliquity of Neptune and the phase of its rotation at encounter combined serendipitously so that the spacecraft entered the magnetosphere at a time when the polar cusp region was directed almost precisely sunward. Within 4 R(N), the magnetic field representation must include localized sources or higher order magnetic multipoles, or both, which are not yet well determined. ![]() The OTD dipole moment is 0.133 gauss-R(N)(3). The planetary magnetic field between 4 and 15 R(N) can be well represented by an offset tilted magnetic dipole (OTD), displaced from the center of Neptune by the surprisingly large amount of 0.55 R(N) and inclined by 47 degrees with respect to the rotation axis. A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10(-5) gauss) was observed near closest approach, at a distance of 1.18 R(N). The detached bow shock wave in the supersonic solar wind flow was detected upstream at 34.9 Neptune radii (R(N)), and the magnetopause boundary was tentatively identified at 26.5 R(N) near the planet-sun line (1 R(N) = 24,765 kilometers). ![]() “There’s more to come.The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. That should provide new intel on the rings’ composition and dynamics, as well as on how Neptune’s clouds and storms evolve, Milam says. Upcoming JWST observations will look at Neptune with other scientific instruments. “JWST was designed to look at the first stars and galaxies across the universe, so we can really see fine details that we haven’t been able to see before,” Milam says. The enormity of the telescope’s mirror also makes its images extra sharp. “The rings have lots of ice and dust in them, which are extremely reflective in infrared light,” says Stefanie Milam, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and one of JWST’s project scientists. A few bright patches mark where high-altitude methane ice clouds reflect sunlight.Īnd then there are the ever-elusive rings. That’s because methane gas in the planet’s atmosphere absorbs much of its infrared light. Neptune itself appears mostly dark in the new image. Neptune’s elusive rings appear as thin arcs of light in this 1989 image from the Voyager 2 spacecraft, taken shortly after the probe made its closest approach to the planet. That’s when the James Webb Space Telescope, or JWST, turned its sharp, infrared gaze toward the planet from roughly 4.4 billion kilometers away ( SN: 7/11/22). In those photos, taken in visible light, the rings appear as thin, concentric arcs.Īs Voyager 2 continued to interplanetary space, Neptune’s rings once again went into hiding - until July. ![]() The last time anyone saw Neptune’s rings was in 1989, when NASA’s Voyager 2 spacecraft, after tearing past the planet, snapped a couple grainy photos from roughly 1 million kilometers away ( SN: 8/7/17). Unlike the dazzling belts encircling Saturn, Neptune’s rings appear dark and faint in visible light, making them difficult to see from Earth. The stunning portrait is a huge improvement over the rings’ previous close-up, which was taken more than 30 years ago. In an infrared image released September 21, Neptune and its gossamer diadems of dust take on an ethereal glow against the inky backdrop of space. Humankind is seeing Neptune’s rings in a whole new light thanks to the James Webb Space Telescope. ![]()
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