nasa s hubble space telescope has discovered a new moon orbiting the distant blue green planet neptune the 14th known to be circling the giant planet the moon designated s 2004 n 1 is estimated to be no more than 12 miles across making it the smallest known moon in the neptunian system it is so small and dim that it is roughly 100 million times fainter than the faintest star that can be seen with the naked eye it even escaped detection by nasa s voyager 2 spacecraft which flew past neptune in 1989 and surveyed the planet s system of moons and rings mark showalter of the seti institute in mountain view calif found the moon july 1 while studying the faint arcs or segments of rings around neptune the moons and arcs orbit very quickly so we had to devise a way to follow their motion in order to bring out the details of the system he said it s the same reason a sports photographer tracks a running athlete the athlete stays in focus but the background blurs the method involved tracking the movement of a white dot that appears over and over again in more than 150 archival neptune photographs taken by hubble from 2004 to 2009 on a whim showalter looked far beyond the ring segments and noticed the white dot about 65 400 miles from neptune located between the orbits of the neptunian moons larissa and proteus the dot is s 2004 n 1 showalter plotted a circular orbit for the moon which completes one revolution around neptune every 23 hours the hubble space telescope is a cooperative project between nasa and the european space agency nasa s goddard space flight center in greenbelt md manages the telescope the space telescope science institute in baltimore md conducts hubble science operations stsci is operated by the association of universities for research in astronomy inc in washington 