October 10 – Discovery of Neptune’s moon, Triton (1846)

Discovered on October 10th 1846 by William Lassell, (who was living and working at that time in West Derby, Liverpool), the Solar System’s biggest retrograde moon Triton, aka Neptune I, is, at 1,353 km radius (approx) the largest satellite of Neptune.

Triton from Voyager 2 (image: NASA)
Triton from Voyager 2 (image: NASA)

Lassell wasn’t daft.  The massive Neptune itself had only been discovered 17 days previously, so where else was he going to be looking for moons?

Current thinking is that Triton is a captured Kuiper Belt Object.  It has a thin atmosphere of mostly nitrogen, with a little methane mixed in, and is, like our own Moon, locked in a synchronous orbit, meaning it always keeps the same face pointing toward its parent (or possibly in this case “adoptive parent”).

Triton (image credit: NASA/JPL-Caltech)
Triton (image credit: NASA/JPL-Caltech)


1868  –  Discovery of asteroid 106 Dione by J C Watson.

1874  –  Discovery of asteroid 139 Juewa, also by J C Watson.

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