Neptune's pair of new moons brings the planet's total count up ... is the faintest moon ever discovered by ground telescopes with a size of only 9 miles (14 km) and a vast orbit of nearly 27 ...

However, it is the fainter Neptune moon, provisionally named S/2021 N1, that presents a unique challenge. With a size of approximately 14 kilometers and an orbit spanning almost 27 years ...

Charon is large in size relative to Pluto, and is locked in a tight orbit with the dwarf planet. A new simulation suggests how it ended up there.