Big, blue, and blustery, distant Neptune is the outermost “real” planet in our solar system — a frigid gas giant nearly 3 billion miles from Earth orbiting the Sun with a handful of faint ring segments and a retinue of 13 moons… um, on second thought, better make that 14.
This composite Hubble Space Telescope picture shows the location of a newly discovered moon, currently designated S/2004 N 1, orbiting the giant planet Neptune.
The moon is so small (no more than 12 miles across) and dim, it was missed by NASA’s Voyager 2 spacecraft cameras when the probe flew by Neptune in 1989. Several other moons that were discovered by Voyager appear in the monochrome 2009 image above, along with the circumplanetary structures known as ring arcs. (The color inset image of Neptune was also taken by Hubble in 2009.)
Mark Showalter of the SETI Institute in Mountain View, Calif., discovered the moon on July 1, while studying the faint ring-arcs of 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,” he said. “It’s the same reason a sports photographer tracks a running athlete — the athlete stays in focus, but the background blurs.”
S/2004 N 1 is located 65,400 miles (105,250 km) from Neptune, and completes one orbit every 23 hours. Don’t expect to spot it in your backyard telescope though… it’s so dim that it’s a hundred million times fainter than the faintest star that can be seen with the naked eye!
(Now all we need to do is settle on a suitable name… any suggestions?)
Credit: NASA, ESA, and M. Showalter (SETI Institute)