Hubble Beams Back Images Of Neptune's Newest Moon Hippocamp


After years of painstaking research, scientists have confirmed that S/2004 N1, now officially called Hippocamp, is the 14th moon of Neptune.

The satellite is only about 34 kilometers in diameter and floats about 105,250 kilometers away from the ice giant. It completes one revolution around Neptune every 23 hours.

Hippocamp is the smallest known moon of Neptune.

Discovery Of Hippocamp

Hippocamp was first photographed in 2004, but it was not until 2013 that it was discovered. Mark Showalter of the SETI Institute pored over 150 archival photos of Neptune taken by the Hubble Space Telescope from 2004 to 2009 and noticed the same white dot making an appearance over and over again.

However, to make the moon's status official, more observations were needed. Showalter and his team devised a technique that allowed them to get a better look at S/2004 N1 and its relationship with Neptune's six other inner moons discovered by Voyager 2 during a flyby in 1989.

Details of the new analysis of Hippocamp appears in the journal Nature.

Hippocamp is named after a half-horse, half-fish creature from Greek mythology. The rules of the International Astronomical Union states that the moons of Neptune should be named after characters from Greek and Roman mythology associated with the sea.

Hippocamp's Violent Past

The scientists also noticed that Hippocamp is unusually close to its neighbor Proteus, a much larger moon, with a distance of only 12,000 kilometers between the two.

Like Earth's own moon, Proteus is inching away from Neptune, which suggests that at some point, it was probably much closer to Hippocamp. Proteus should have gobbled Hippocamp up, the team stated.

The existence of Hippocamp probably means that it is a younger moon formed after a larger moon had collided with a comet, billions of years ago.

The theory was supported by an image taken by Voyager 2 in 1989 that revealed a large impact crater on the surface of Proteus.

"In 1989, we thought the crater was the end of the story," stated Showalter. "With Hubble, now we know that a little piece of Proteus got left behind and we see it today as Hippocamp."

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