New Neptune Moon
July 15, 2013

New Neptune Moon Discovered Brings Count To 14

Lee Rannals for - Your Universe Online

According to NASA, the Hubble Space Telescope has revealed that Neptune has been hiding another moon, bringing the total count of moons orbiting the planet to 14.

The new moon, named S/2004 N 1, is no more than 12 miles across, making it the smallest known moon in the Neptunian system. NASA said this moon is so small that it is about 100 million times fainter than the faintest star that can be seen with the naked eye. The moon is so small that it even eluded NASA's Voyager 2 spacecraft as it flew past Neptune in 1989 and surveyed the planet.

"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," said Mark Showalter of the SETI Institute in Mountain View, California. "It's the same reason a sports photographer tracks a running athlete - the athlete stays in focus, but the background blurs."

Showalter discovered the moon while looking beyond the ring segments. He noticed a white dot about 65,400 miles from Neptune between the orbits of the Neptunian moons Larissa and Proteus.

The astronomers analyzed over 150 archival Neptune photographs taken by Hubble from 2004 to 2009, finding that the same white dot appeared over and over again. Showalter plotted a circular orbit for the moon and determined that it completes one revolution around Neptune every 23 hours.

NASA said that many of Neptune's moons seen orbiting the planet probably formed after the largest moon Triton settled into its retrograde orbit. Scientists believe Triton, which is nearly the size of Earth's moon, may be a captured icy dwarf planet from the Kuiper Belt at the outer rim of the solar system. When Neptune captured this moon, it would have gravitationally torn apart any original satellite system Neptune possessed at the time.

Scientists say Triton has a density of 2.0 and is probably about 25 percent water ice with the remainder being rocky material. The moon contains a tenuous nitrogen atmosphere with small amounts of methane. When Voyager 2 passed by Triton 24-years-ago, the probe witnessed numerous volcanoes erupting liquid nitrogen dust, or methane compounds from beneath the surface in plumes up to five miles high. This volcanic activity is thought to be driven by seasonal heating from the Sun.