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The dance of Neptune's water sprite moons

27 Aug 2020, 13:00 UTC
The dance of Neptune's water sprite moons
(200 words excerpt, click title or image to see full post)

Neptune is an interesting planet. And that’s a little irritating, because it’s so far away that it’s really hard to observe it in detail. It’s 30 times farther from the Sun than Earth, which means it gets only 1/900th as much light as we do (and then it reflects that light and sends it back to us, dimming it further). Studying its moons is even harder because they’re so much smaller and subsequently fainter.

But, despite that, some astronomers wanted to investigate the moons to see what they could figure out about their orbits. That can sometimes tell you a lot about the history of the moons (like it did for Neptune’s moon Hippocamp).

In this case, a team looked at dinky Naiad and Thalassa, both elongated potatoes about 100 km in length (and named after Greek water deities, after Neptune’s role as god of the sea). They’re the innermost Neptunian moons known, with very nearly circular orbits 48,200 and 50,075 km from Neptune’s center (which is the usual way to measure orbital size; Neptune has a radius just under 25,000 km). If both these moons orbited in the same plane they’d pass less than 2000 km from each other. ...

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