Galatea and Ring Arcs
Date: 1 Jul 1989

Neptune's moon Galatea and new ring arcs, or partial rings, were discovered in the same month by the Voyager 1 science team. Galatea was initially called S/1989 N4 until its discovery was confirmed.


The 155 second exposure taken by Voyager's narrow-angle camera shows the glare of an overexposed Neptune to the right of the moon and ring arc. The two bright streaks below the moon and ring arc are stars.


The ring arc is approximately 50,000 km (or 30,000 miles) long. (The second ring arc, not apparent here, is approximately 10,000 km (6,000 miles) long and is associated with the moon Despina.)


The ring arc, along with Galatea, orbits about 62,000 km (38,000 miles) from the planet's center, or about 37,000 km (23,000 miles) from the planet's cloud tops.


Astronomers have long suspected the existence of such an irregular ring system around Neptune. Data from repeated ground based observations hinted at the existence of irregular strands of partial rings orbiting Neptune. Voyager's photographs of the ring arcs are the first photographic evidence that such a ring system exists. Voyager scientists said the ring arcs may be comprised of debris associated with the nearby moons, or may be the remnants of moons that have been torn apart or ground down through collisions.


Last Update: 17 Jun 2011 (AMB)

Credit: NASA/JPL