3rd Moon Found Orbiting Neptune

A new moon of Neptune, about one-fifth the size of Earth’s moon, has been discovered in photographs taken by the Voyager 2 space probe, Jet Propulsion Laboratory researchers said today. Only two moons, Nereid and Triton, were previously known.

The new moon, temporarily designated 1989 N1, is as large as 400 miles in diameter and orbits Neptune’s equator at an altitude of about 57,000 miles. It was discovered by JPL astronomer Stephen P. Synnott as a “small, bright smudge” on photographs of the giant blue-green planet. The photographs were taken from 57 million miles away as the probe raced toward its Aug. 24 rendezvous with Neptune and Triton.

Subsequent photographs showed the moon in different positions corresponding to the predicted orbit, confirming that the object is a moon.

Earlier photographs from Voyager had revealed the existence of a large “dark spot” on Neptune similar to the giant red spot on Jupiter and believed to be caused by weather conditions. The photographs have also revealed dark bands near the poles similar to those seen on other gaseous planets.

The new moon, which is too faint to appear in printed photographs, is the first of as many as 10 that researchers expect to find circling Neptune.