William Lassel, the British merchant and astronomer, who first discovered Neptune’s largest moon, Triton (just 17 days after Neptune itself was discovered by a German astronomer), also suggest the possibility of rings around the planet, though his findings were largely dismissed as an illusion (which it likely was). Some evidence of a ring was found in 1966, when the planet passed in front of a star and an extra “blink” was detected, but not until a decade later when Uranus’s rings were discovered the same did the possibility of rings around Neptune began to be seriously entertained.

On this day, August 22, in 1989, the Voyager 2 spacecraft, on its way to the outer reaches of the solar system, discovered a system of rings around Neptune.

The faint outer ring arc is named Adams, and contains within it three prominent arcs, named “Liberty,” “Equality,” and “Fraternity” by their French discoverers in 1984. Scientists still are not sure how the rings maintain their shape, as the laws of motion suggest they should have broken up by now. Current theory suggests the rings may be affected by the the planet’s “shepherd” moon Despina.