The Hubble Space Telescope, a collaborative project between NASA and the European Space Agency, has uncovered a new moon orbiting Neptune. This is the 14th moon known to be circling the planet and is described by Hubble as “no bigger than a metropolitan city.”
At just 20 kilometres in diameter, S/2004 N 1 is certainly the smallest known moon to orbit Neptune, and is estimated to be 100 times fainter than the faintest star that can be seen with the naked eye. In fact, NASA’s Voyager 2 spacecraft flew by the planet in 1989 and, despite making other discoveries, failed to detect Neptune’s 14th moon.
Astronomer Mark Showalter of the SETI Institute discovered the moon on July 1, while studying the arcs and rings surrounding Neptune: “The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring about the details of the system.”
It was while completing this detailed study that Showalter spotted a white dot approximately 105,251 kilometres from Neptune. With the help of over 150 archival Neptune photographs taken by the Hubble Space Telescope, Showalter was able to determine that the white dot was, in fact, a moon.
S/2004 N 1 reportedly completes one revolution around Neptune every 23 hours.