Wikijunior:Solar System/Neptune/Nereid

Nereid from Voyager 2 spacecraft

Nereid is a moon of the planet Neptune. It is sometimes called "Neptune II". We still do not know much about this moon. Because it has an unusual orbit, scientists think that it may have been an asteroid that was captured by Neptune's gravity.

How big is Nereid?

This is the third largest of the moons of Neptune, but it is only 340 km across

How long is a day on Nereid?

A day on Nereid is 11 and a half hours.

How much would Nereid's gravity pull on me?

Nereid is only a small moon that has very low gravity.

Newtons describe how hard gravity is pulling you down. On Earth, if you weigh 51 kilograms or 112 pounds, your weight is 500 newtons. We only use newtons for some special purposes, when we are really interested in how hard we push down on something because gravity is pulling us.

Your weight in newtons would be much less on Nereid, only about 1/137 what it is on Earth. A typical adult would weigh about half a newton. But then you'll have to add in the weight of your spacesuit as well, because that is pressing down on the surface just like you are.

Who is it named after?

This moon was named for the sea-nymphs from Greek mythology. A nymph is a nature spirit that looks like a beautiful woman.

How was it discovered?

It was discovered in 1949 by the astronomer Gerard P. Kuiper.