NASA Hubble Space Telescope Discovers New, Tiny Moon Orbiting Neptune

About 2.8 billion miles from the sun is Neptune, the dark, cold planet whipped by supersonic winds. The last of the hydrogen and helium gas giants in our solar system, the planet appears to be a bright blue in color. Now, researchers have found out something more about this planet; NASA's Hubble Space Telescope has discovered a new moon orbiting Neptune.

Neptune was once thought to only possess 13 moons, six of which were discovered by Voyager 2. The largest of these, called Triton, orbits the planet in the opposite direction of the other moons; this suggests that it may have been "captured" by the planet in the distant past.

In comparison to Triton, the newly discovered moon is tiny. Named S/2004 N 1, it's estimated to be no more than 12 miles across. In fact, this makes it the smallest known moon in the Neptunian system. It's about 100 million times fainter than the faintest star that can been seen with the naked eye, which explains how it managed to remain undetected for so long--even when NASA's Voyager 2 spacecraft flew past Neptune in 1989.

"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 a news release. "It's the same reason a sports photographer tracks a running athlete-the athlete stays in focus, but the background blurs."

So how did they detect the moon? The researchers used a technique that involved tracking the movement of a white dot that appears over and over again in more than 150 archival Neptune photographs that were taken by Hubble over a period of about five years.  The researchers found that this white dot was located about 65,400 miles from Neptune between the orbits of the moons, Larissa and Proteus. With a circular orbit, the new moon completes one revolution around Neptune every 23 hours.

The findings show a little bit more about Neptune and also reveal how the increasing precision of instruments are allowing astronomers to find more and more about our solar system and the universe.