PJS@GROUCH.JPL.NASA.GOV (Peter Scott) (07/21/89)
Excerpted without permission from NASA _Voyager Bulletin_, Mission Status Report No. 88, July 12: ADD A NEW NEPTUNIAN MOON A new moon has been discovered orbiting Neptune. Temporarily designated 1989 N1, the new moon was initially seen in images transmitted to Earth by Voyager 2 in mid-June. Its existence was confirmed upon examination of other images after the moon's orbital motion had been calculated and its position could be predicted. The new Neptunian satellite could range in diameter from 200 to 600 km (about 125 to 400 miles) and oribts in a very nearly circular and equatorial orbit about 92,700 km (about 57,600 mi) from the planet's cloud tops (or about 117,500 km) (73,000 mi) from the planet's center). A permanent name will be given to the moon at a later date by the International Astronomical Union (IAU). According to Dr. Stephen P. Synnott, a Voyager imaging team scientist at JPL, the satellite appeared as a small, bright smudge in Voyager pictures due to the long (46-second) exposure. At this point, the moon is too indistinct to appear in photographic prints made from the Voyager images. Pictures taken in coming weeks will show the moon more clearly. 1989 N1 cannot be seen from Earth because the moon is so close to Neptune that the brightness of the planet itself masks the tiny point of light. Voyager 2 will continue to study the moon and will conduct searches for others on approach to the planet. [...] The moon orbits well outside the orbits of the postulated ring arcs. Its existence lessens concerns about radiation hazards to the spacecraft near the planet, since the moon probably sweeps charged particles out of the area as it orbits Neptune. Peter Scott (pjs@grouch.jpl.nasa.gov, speaking only for myself)