Neptune is the only planet in the Solar System not visible to the naked eye and the first predicted by mathematics before its discovery. Located 30 times farther from the Sun than Earth, Neptune orbits in the remote, dark region of the outer Solar System.Īt that extreme distance, the Sun is so small and faint that high noon on this giant planet is similar to a dim twilight on Earth. The menagerie of moons in our solar system is rich and wondrous, but it’s only a taste of what else is out there.This image, taken with Webb’s Near-Infrared Camera (NIRCam), shows Neptune, its dusty rings, and seven moons. Its discoverers believe that it isn’t a rocky or icy world like the moons we’re used to, but a massive, swirling ball of gas about the size of Neptune. Astronomers think they may have already found their first exomoon, as they’re called, orbiting a planet about 8,000 light-years away from Earth.Īt that distance, the moon doesn’t show up in telescope images at all it is seen instead in the slight wobble of the planet it orbits, tugging at it as it goes. The search for new moons extends beyond the solar system, to other stars and planets. Their names are still being considered, and will be approved by the International Astronomical Union’s Minor Planet Center, the organization in charge of confirming such discoveries. Like Hippocamp, the objects appear as tiny glints of light in telescope observations. Last summer, astronomers announced the addition of 10 new moons around Jupiter, bringing its total to 79, the most in the solar system. But they are still finding new neighbors. Astronomers certainly have a more intimate understanding of our cosmic home than they did centuries ago.

Other moons are likely lurking out there, waiting to be found. Hippocamp orbits there, too, but the spacecraft missed it. Voyager 2 spotted six small moons orbiting close to Neptune in 1989. The rest were discovered in the past 40 years or so, via powerful ground-based telescopes and the Voyager mission, the vaunted NASA program that launched two probes on a tour of the solar system’s farthest planes. More than a century would pass until the next moon, Nereid, was detected, in 1949. The first and largest, Triton, was found less than three weeks after Neptune itself was discovered, in 1846. The moon christening is another milestone in the centuries-long study of Neptune’s moons, which bear the names of mythological figures. Even to Hubble, an extremely powerful instrument, the moon appears as a fuzzy dot in photographs. The moon is too far from Earth to tell scientists have said that Hippocamp is roughly 100 million times fainter than the faintest star that is visible to the naked eye. So where does Hippocamp fit among the diverse assortment of moons in the solar system? That’s up to the imagination. The team believes that the moon is a chunk of Proteus that broke off after a comet struck. The astronomers suspect that Hippocamp formed as some other moons in the solar system did, including ours-through a violent collision. It orbits close to its moon sibling Proteus, another Neptunian moon, and completes one trip around Neptune about every 23 hours. At 21 miles, or 34 kilometers, across, Hippocamp is about the size of a metropolitan city and the smallest of Neptune’s moons.

Showalter and his colleagues reported new observations of the moon, published Wednesday in Nature, that provide a better measure of its size and orbit. Hippocamp is one of 14 moons orbiting Neptune. Now the moon has a formal name: Hippocamp, after the mythological sea creatures that galloped alongside the Roman god Neptune. To investigate, he dove into a cache of photographs, five years’ worth, examining each one to see if it had that spark of intrigue. Mark Showalter, a scientist at the SETI Institute, noticed a mysterious white dot in observations of Neptune taken by the Hubble Space Telescope, NASA’s best eyes on the solar system and beyond. In 2013, astronomers found something new around Neptune, in a manner that would make Marie Kondo proud. They feel as familiar as the planets they orbit. Many moons are well studied, their features documented in astounding detail. Io, another moon of Jupiter, is molten, its surface constantly redrawn by flowing lava.Īstronomers have observed these and other moons for centuries, first with homemade telescopes and now with million-dollar spacecraft.

Enceladus, of Saturn, and Europa, of Jupiter, are frozen, shrouded in a thick layer of ice with a liquid-ocean center. Our own moon is a barren, rocky world coated with craters. There are hundreds, and they come in all kinds of varieties, like a cosmic tray of assorted chocolates. The planets may get top billing in the solar system, but they are far outnumbered by the moons.

Neptunes moons