NASA and SETI discover new Neptunian moon, spot what Voyager 2 missed

A baker's dozen worth of moons might already sound like too many for us Earthlings, but Neptune has just had its count bumped to 14. Though the extra luna appeared as a white dot in over 150 photos taken by NASA's Hubble telescope between 2004 and 2009, it took SETI's Mark Showalter to discover it after poring over images of faint rings around the planet. Dubbed S/2004 N 1, the satellite is no more than 12 miles across and completes its orbit every 23 hours. Hoping to spot it in the night sky? You're better off hitting the second source link for more pictures, as it's 100 million times dimmer than the faintest star viewable with the naked eye, and it escaped Voyager 2, to boot.

[Image credit: NASA, ESA and A. Feild (STScI)]

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NASA Hubble Finds New Neptune Moon

WASHINGTON -- 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 (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy Inc., in Washington.