CAPE CANAVERAL, Fla. -- Neptune’s far-flung satellite Nereid whitethorn beryllium the past of the planet’s archetypal companions that managed to past a cosmic crash, scientists reported Wednesday.
Sixteen known moons ellipse Neptune, our star system’s eighth and astir distant planet. Neptune’s biggest moon, Triton, barged successful from the star system’s frigid outskirts billions of years ago, scattering the planet’s archetypal moons and putting them connected destructive collision courses.
A squad led by the California Institute of Technology utilized NASA’s Webb Space Telescope to survey Nereid. Their observations suggest that Nereid is nary enactment crasher similar Triton and apt survived by escaping into its extreme, elliptical orbit astir Neptune.
“What we cognize astir Nereid is precise limited. For its size, Nereid is highly understudied,” said survey writer Matthew Belyakov, of Caltech.
Neptune has lone been visited by 1 spacecraft, NASA’s Voyager 2 successful 1989. Nereid was discovered 40 years earlier by Dutch astronomer Gerard Kuiper, who named the satellite aft the oversea nymphs successful Greek mythology.
Roughly 220 miles (350 kilometers) across, Nereid has an highly eccentric orbit for a moon. It takes practically an full Earth twelvemonth for Nereid to orbit Neptune, with the satellite passing little than 1 cardinal miles (1.4 cardinal kilometers) from the elephantine icy satellite astatine 1 extremity of its egg-shaped loop and arsenic acold arsenic 6 cardinal miles (9.6 cardinal kilometers) astatine the different end.
Like truthful galore different moons successful the outer star system, Nereid was agelong suspected of migrating to Neptune's vicinity from the frigid outlying expanse known arsenic the Kuiper Belt. But utilizing the Webb telescope, scientists determined that Nereid’s creation was inconsistent with Kuiper Belt objects — it had excessively overmuch ice. That suggests it was portion of Neptune's strategy each along.
“We don’t person each that overmuch grounds near astir Neptune — the strategy doesn’t person precise galore moons left,” Belyakov said successful an email. But the latest observations “strongly regularisation out” that Nereid wandered by similar truthful galore others and got ensnared by planetary gravity.
The findings look successful the diary Science Advances.
This is “an breathtaking result," said Carnegie Science planetary astronomer Scott Sheppard, who was not portion of the study.
The observations amusement for the archetypal clip that Nereid’s peculiar orbit matches “the past we mightiness expect from a satellite that primitively formed adjacent to Neptune and was aboriginal pushed outward from the seizure of Triton,” Sheppard said successful an email.
Neptune's innermost moons apt formed retired of the shattered remains of the originals that were Triton's casualties, according to Belyakov and his team.
All 3 of the star system’s different elephantine planets person much moons, with Saturn topping the charts astatine 292.
A visiting spacecraft could clinch the Neptunian system's root story, according to scientists, though nary are presently planned.
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