Mark Showalter, an astronomer at the SETI Institute, was browsing old photos of Neptune taken by the Hubble Space Telescope several years ago when he noticed a tiny white dot in about 150 different images. He was actually looking at a previously undiscovered moon around the other blue planet in our solar system.
With a provisional title of “S/ 2004 N1”, this tiny moon measures only 12 miles (19km) wide and is 100 million times fainter than the dimmest known star when observed by the human eye. To put this in perspective, Neptune’s largest moon is Titron at 1680 miles (2700km). It is so small that it missed detection by NASA’s Voyager 2 when the craft thoroughly observed Neptune and its moons in 1989.
The examination of the planet and its surroundings in 1989 unveiled six new moons, but not S/ 2004 N1 because this tiny moon passed detection during NASA’s initial study of Voyager 2’s data. This is because the moons and rig segments orbit Neptune very quickly. “It’s the same reason a sports photographer tracks a running athlete- the athlete stays in focus, but the background blurs,” said Showalter when commenting on his discovery of the new moon.
By plotting a circular orbit of the moon, Showalter and his team predicted a 23 hour orbit of this moon around Neptune. Its position at about 6,000 miles from the blue planet places “S/ 2004 N1” between some of Neptune’s other moons, Larissa and Proteus (the 7th and 8th largest moons around this planet, respectively).
Naming the new moon will take time. Showalter and his group are deciding on a title which they will then submit to the International Astronomical Union, who will make the final decision. “What I can say is that the name will be out of Roman and Greek mythology and it will have to do with characters who are related to Neptune, the god of the oceans,” commented the astronomer.
The discovery of the new moon on July 1st has prompted a paper on the achievement to be published later this year.