Hippocamp, also designated Neptune XIV, is a small inner moon of Neptune discovered on 1 July 2013. It was found by astronomer Mark Showalter by analyzing archived Neptune photographs the Hubble Space Telescope captured between 2004 and 2009. The moon is so dim that it was not observed when the Voyager 2 space probe flew by Neptune and its moons in 1989. It is about 35 km (20 mi) in diameter, and orbits Neptune in about 23 hours, just under one Earth day. Due to its unusually close distance to Neptune's largest inner moon Proteus, it has been hypothesized that Hippocamp may have accreted from material ejected by an impact on Proteus several billion years ago. The moon was previously known by its provisional designation S/2004 N 1 until it was officially named Hippocamp in February 2019, after the mythological sea-horse symbolizing Poseidon in Greek mythology.
History
Discovery Hippocamp was discovered by a team of astronomers led by Mark Showalter of the SETI Institute on 1 July 2013. Showalter was examining archival Hubble Space Telescope images of Neptune from 2009, as part of his study on the ring arcs of Neptune. Since the inner moons and ring arcs of Neptune orbit quickly, Showalter developed and used a technique similar to panning, where multiple short-exposure images are gathered and digitally warped to compensate for orbital motion and to allow stacking of multiple images to bring out faint details. On a whim, Showalter decided to extend his analysis to regions beyond Neptune's ring system; he then found Hippocamp as a faint but unambiguous white dot. To confirm the moon, Showalter further analyzed over 150 archival Hubble images going back to 2004. Within a week, Showalter repeatedly found Hippocamp in these images and was able to identify the moon at ten different observation times from 2004 to 2009. Showalter had also checked images from the Voyager 2 spacecraft to find any detections of Hippocamp during its 1989 Neptune flyby, but was unable to identify the moon since it was too dim to be detected by Voyager 2's cameras. Nonetheless, the number of archival Hubble images with Hippocamp was enough to determine the moon's orbit. The discovery of Hippocamp was formally announced in a notice issued by the International Astronomical Union's Central Bureau for Astronomical Telegrams, along with a press release by the Space Telescope Science Institute on 15 July 2013. Given that the relevant images examined by Showalter were available to the public, the discovery could have been made by anyone.
Naming The moon is named after the hippocampus, a mythological creature depicted as having the upper body of a horse with the lower body of a fish in Greek mythology. The hippocampus symbolizes the Greek sea god Poseidon as well as the Roman sea god Neptune. In Roman mythology, Neptune would often drive a sea-chariot pulled by hippocampi. The moon was given the provisional designation S/2004 N 1 when it was announced. The provisional designation indicates that it was the first Neptunian satellite identified in images dating from 2004. Follow-up Hubble observations of Hippocamp were conducted by Showalter in 2016, and the moon was later given its permanent Roman numeral designation by the Minor Planet Center after its recovery. Hippocamp was given the Roman numeral designation of Neptune XIV (14) on 25 September 2018, though it remained without an official name until February 2019. By the International Astronomical Union's (IAU's) nomenclature guidelines, name proposals for Neptune's moons must be based on a figure from Greco-Roman mythology with a relationship to Poseidon or Neptune. Showalter and his team had sought for names since the announcement of their discovery; among the names considered was Polyphemus, the gigantic one-eyed son of Poseidon and Thoosa. Showalter then settled on the name Hippocamp in acknowledgement of the seahorse genus, Hippocampus, mainly for his passion for scuba diving and the animal itself. Showalter's name proposal was approved by the IAU's naming committee on 20 February 2019, and the name was announced in a press release by the Space Telescope Science Institute.
Origin
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