Neptune is the 8th planet from the sun at nearly 2.8 million miles, or 30 times as far away as earth, and makes a rotation around the sun every 165 years. It was the first planet to be located through mathematical predictions rather than through regular observations of the sky on September 23, 1846, by Johann Gotfried Galle.
Neptune had 13 known moons until NASA’s recent discovery, using the Hubble Space Telescope. The largest of Neptune’s moons is Triton, which rotates in a direction opposite of it’s planet and measures approximately 1,680 miles across. Because it rotates in this manner, many scientists believe that Triton was originally a dwarf planet that was sucked into Neptune’s orbit. “This capture would have gravitationally torn up any original satellite system Neptune possessed,” Hubble officials wrote in a statement. “Many of the moons now seen orbiting the planet probably formed after Triton settled into its unusual retrograde orbit about Neptune.”
The newly discovered moon, classified as S/2004 N 1, is now considered to be the smallest known moon to be rotating around Neptune, measuring approximately 12 miles across. It is so small that
S/2004 N 1 was discovered on July 1, 2013, while Mark Showalter of the SETI Institute was studying Neptune’s segments of rings, or arcs. “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,” Showalter said. “It’s the same reason a sports photographer tracks a running athlete — the athlete stays in focus, but the background blurs.” There was a small white dot that appeared in over 150 photographs of Neptune, taken by Hubble Space Telescope, from 2004 to 2009. Showalter tracked the movements of this dot throughout all of the photographs that were taken, before finally making the shocking discovery. He also determined that the small moon orbits the planet every 23 hours.
The procedure I devised predicts where any given moon ought to move from one image to the next, and then combines the images with a ‘twist’ that compensates for the expected motion. I developed this procedure (and I am certainly not the first) to study some peculiar arcs in the rings of Neptune. However, I soon realized it could be useful for moons as well. It was only when I expanded my analysis out to regions well beyond Neptune’s ring system that an extra little dot turned up, over and over again.