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ScienceSpace

Neptune's New Moon — S/2004 N 1 — 14th Moon Of Neptune Discovered

A new moon was recently discovered orbiting Neptune by NASA’s Hubble Space Telescope — which means that there are now 14 known moons orbiting the distant blue-green gas-giant.

"This diagram shows the orbits of several moons located close to the planet Neptune. All of them were discovered in 1989 by NASA's Voyager 2 spacecraft, with the exception of S/2004 N 1, which was discovered in archival Hubble Space Telescope images taken from 2004 to 2009. The moons all follow prograde orbits and are nestled among Neptune's rings (not shown). The outer moon Triton was discovered in 1846 — the same year the planet itself was discovered. Triton's orbit is retrograde, suggesting it is a captured Kuiper Belt object and therefore a distant cousin of Pluto. The inner moons may have formed after Triton's capture several billion years ago." Image Credit: NASA, ESA, and A. Feild (STScI)
“This diagram shows the orbits of several moons located close to the planet Neptune. All of them were discovered in 1989 by NASA’s Voyager 2 spacecraft, with the exception of S/2004 N 1, which was discovered in archival Hubble Space Telescope images taken from 2004 to 2009. The moons all follow prograde orbits and are nestled among Neptune’s rings (not shown). The outer moon Triton was discovered in 1846 — the same year the planet itself was discovered. Triton’s orbit is retrograde, suggesting it is a captured Kuiper Belt object and therefore a distant cousin of Pluto. The inner moons may have formed after Triton’s capture several billion years ago.”
Image Credit: NASA, ESA, and A. Feild (STScI)

The new moon — S/2004 N 1 — is tiny, being no larger than 12 miles across, which makes it the smallest moon currently known of within the Neptunian system. The size and dimness is the reason that the moon has remained undiscovered for so long — it’s around 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.”

The moon was discovered by Mark Showalter of the SETI Institute in Mountain View, California, on July 1, while researching 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. 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.”




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