Neptune’s third largest moon, Nereid, was discovered on May 1st, 1939, by Gerard P Kuiper, using the 83-inch Otto Struve Telescope at Mcdonald Observatory, Texas. It is about 170 km in diameter, and has a day lasting just 11.5 hours, but a year almost identical to ours, at 360 days.
Nereid has a prograde rotation, and a very eccentric orbit, which takes it from 853,000 miles at periapsis to 5,999,000 miles at apoapsis. This has led astronomers to believe it is either a captive asteroid (or Kuiper Belt Object) or has had a previously more normal orbit changed by the capture of Triton.
The Nereids after whom this moon is named were the fifty daughters of Nereus and Doris. They were sea nymphs who attended Neptune (he married one of them, Amphitrite, who bore his son Triton.