Even in today’s age of far-flung spacecraft and enormous telescopes, the solar system is still a largely uncharted realm of undiscovered wonders. Earlier this month, two new natural satellites were confirmed orbiting Jupiter, bringing the gas giant’s total number of confirmed moons up to 69.
The two new moons, like many small objects in the solar system, have not been named yet beyond the notation indicating their discovery date: S/2016 J 1 and S/2017 J 1 (S for “satellite” and J for “Jupiter”). The moons, both estimated at about 2 km in diameter, were discovered by a team led by astronomer Scott Sheppard of the Carnegie Institution for Science. Sheppard was actually looking for objects in the outer solar system—in the Kuiper belt and beyond—when Jupiter aligned with two telescopes the Carnegie Institution operates in the Atacama Desert of Chile.
Advertisement – Continue Reading Below
“We were continuing our survey looking for very distant objects in the outer solar system, which includes looking for Planet X, and Jupiter just happened to be in the area we were looking in 2016 and 2017,” Sheppard told Sky and Telescope.
Like the majority of Jupiter’s small satellites, both the newly-discovered moons are in a retrograde orbit, meaning they orbit Jupiter in the opposite direction that Jupiter rotates on its axis. The two moons also have a high degree of inclination, about 140 to 150 degrees off the orbital plane of Jupiter. These two clues tell astronomers that S/2016 J 1 and S/2017 J 1 were likely captured by Jupiter when they strayed too close to the massive gravitational pull of the biggest planet in the solar system.
Both moons have highly elongated orbits that take them far away from Jupiter, as S/2016 J 1 orbits at an average distance of 20,600,000 km and S/2017 J 1 orbits 23,500,000 km from the host planet. Though S/2016 J 1 was first spotted in early 2016, the orbit could not be determined until follow-up observations were made six weeks ago with the 8.2-m Subaru telescope on Mauna Kea in Hawaii.
Sheppard’s work has also helped planetary scientists relocate some of Jupiter’s so-called “lost moons.” Eleven small Jovian moons with unknown orbits have been discovered, but astronomers have been unable to reliably locate them due to a lack of information.
“We have for sure recovered five of the lost moons,” Sheppard told Sky and Telescope. “We have several more Jupiter moons in our new 2017 observations and likely have all of the lost moons in our new observations.”
There is still plenty to discover in our little celestial neighborhood.
Source: Sky and Telescope