The solar system's largest planet has some "new" neighbors.

Astronomers have discovered 12 additional moons orbiting Jupiter, bringing the total to 79, the most of any planet in the solar system, a new study found.

The moons were discovered while astronomers were searching for objects at the edge of the solar system, according to Scott Sheppard, a scientist at the Carnegie Institution for Science who co-authored the study.

“Jupiter just happened to be in the sky near the search fields where we were looking for extremely distant solar system objects, so we were serendipitously able to look for new moons around Jupiter while at the same time looking for planets at the fringes of our solar system,” Sheppard said.

One of the objects they were looking for is the mysterious "Planet X" or "Planet Nine," which remains undiscovered.

The discovery of the new moons was reported Tuesday in the Minor Planet Electronic Circular, a publication of the International Astronomical Union.

Researchers say the new Jupiter moons weren’t seen before because they are tiny – the biggest ones are only about two miles across.

One of the newly discovered moons is an "oddball," Sheppard said. "It has an orbit like no other known Jovian moon,” he explained. It orbits in an opposite direction from the other moons near it, meaning head-on collisions are much more likely to occur.

“This is an unstable situation,” said Sheppard. “Head-on collisions would quickly break apart and grind the objects down to dust.

“It’s also likely Jupiter’s smallest known moon, being less than one kilometer (0.6 mile) in diameter."

Telescopes in Chile, Hawaii and Arizona were used for the original discovery and year-long confirmation of the moons.

“It takes several observations to confirm an object actually orbits around Jupiter,” said Gareth Williams of the International Astronomical Union’s Minor Planet Center. “So, the whole process took a year.”

Legendary Italian scientist Galileo first detected Jupiter’s four largest moons, Io, Europa, Ganymede and Callisto in 1610. </s> This Hubble telescope image of the giant planet Jupiter reveals the impact sites of two fragments from comet Shoemaker-Levy 9. Twenty-one large chunks of the comet rained down upon Jupiter in July 1994. The impact sites, located in the planet's Southern Hemisphere, are the dark spots in the upper left of the photograph.

The solar system's largest planet has some "new" neighbors.

Astronomers have discovered 12 additional moons in orbit around Jupiter, bringing the total to 79, the most of any planet in the solar system, a new study found.

The moons were discovered while astronomers were searching for objects at the edge of the solar system, according to Scott Sheppard, a scientist at the Carnegie Institution for Science who co-authored the study.

“Jupiter just happened to be in the sky near the search fields where we were looking for extremely distant solar system objects, so we were serendipitously able to look for new moons around Jupiter while at the same time looking for planets at the fringes of our solar system,” Sheppard said.

One of the objects they were looking for is the mysterious "Planet X" or "Planet Nine," which remains undiscovered.

The discovery of the new moons was reported Tuesday in the Minor Planet Electronic Circular, a publication of the International Astronomical Union.

Researchers say the new Jupiter moons weren’t seen before because they are tiny – the biggest ones are only about two miles across.

One of the newly discovered moons is an "oddball," Sheppard said. "It has an orbit like no other known Jovian moon,” he explained. It orbits in an opposite direction from the other moons near it, meaning head-on collisions are much more likely to occur.

“This is an unstable situation,” said Sheppard. “Head-on collisions would quickly break apart and grind the objects down to dust.

“It’s also likely Jupiter’s smallest known moon, being less than one kilometer (0.6 mile) in diameter."

Telescopes in Chile, Hawaii and Arizona were used for the original discovery and year-long confirmation of the moons.

“It takes several observations to confirm an object actually orbits around Jupiter,” said Gareth Williams of the International Astronomical Union’s Minor Planet Center. “So, the whole process took a year.”

Legendary Italian scientist Galileo first detected Jupiter’s four largest moons, Io, Europa, Ganymede and Callisto in 1610. </s> The advent of monster telescopes equipped with super-sensitive, wide-field detectors has been a boon for astronomical discoveries, among them a bevy of tiny moonlets around the outer planets. For example, observations made from 2000 to 2003 yielded 46 moons around Jupiter — more than two-thirds of the planet's total!Now astronomer Scott Sheppard (Carnegie Institution for Science)As Sheppard explains, "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." So they took a minor detour to image some fields that were very close to Jupiter.With magnitudes hovering near 24, these barely-there moonlets must be only 1 or 2 km across. So for now all that's really known is the character of their orbits:Sheppard discovered this moonlet during an observing run on March 8, 2016, with the 6.5-m Magellan-Baade reflector at Las Campanas Observatory in Chile. Averaging 20,600,000 from Jupiter, it's in an elongated orbit inclined 140° with an eccentricity of 0.14. It takes 1.65 years to orbit the planet. ( See Animation Although Sheppard first sighted this moon last year, its orbit remained uncertain until he teamed up with David Tholen (University of Hawai'i) and Chadwick Trujillo (Gemini Observatory), who swept it up six weeks ago with the 8.2-m Subaru reflector on Mauna Kea.Sheppard and Trujillo recorded the second new find on March 23, 2017, using the venerable 4-m Victor Blanco reflector at Cerro Tololo Inter-american Observatory in Chile. It also turned up in images recorded with Subaru in 2016 and earlier this year, which allowed the team to confirm its existence. This moon likewise is far from Jupiter, at an average distance of 23,500,000 km. In this very elongated orbit, inclined 149° with an eccentricity of 0.40, the moonlet takes 2.01 years to go around Jupiter.( See Animation Both of these discoveries, as with the vast majority of Jupiter's moons, occupy retrograde orbits, with inclinations greater than 90°, meaning that they move in directions opposite that of the planet's spin. These distant, irregular orbits imply that these bodies formed elsewhere in the outer solar system and were captured while passing by early in the planet's history.According to an orbital assessment published in April by Marina Brozović and Robert A. Jacobson (Jet Propulsion Laboratory), 11 of Jupiter's irregular satellites have orbits known so poorly that they're considered "lost." Sheppard and his collaborators found all but one of those in 2003, and they haven't been observed since.However, that's changing. The time Sheppard and Trujillo spent scrutinizing the region around Jupiter has already led to the recovery of S/2003 J 5 S/2003 J 15 , and S/2003 J 18 , as well as a better orbit for S/2011 J 2 "We have for sure recovered five of the lost moons," Sheppard says, noting that the 2016 and 2017 observations could be easily linked to some of 2003's uncertain finds. "We have several more Jupiter moons in our new 2017 observations and likely have all of the lost moons in our new observations," he continues, but to ensure the identifications he'll need to return to those big telescopes for more observations in early 2018.If you're interested in all these crazy outer-planet moons, be sure to check out Sheppard's compilations for Jupiter and the other outer planets. </s> This Hubble telescope image of the giant planet Jupiter reveals the impact sites of two fragments from comet Shoemaker-Levy 9. Twenty-one large chunks of the comet rained down upon Jupiter in July 1994. The impact sites, located in the planet's Southern Hemisphere, are the dark spots in the upper left of the photograph.

The solar system's largest planet has some "new" neighbors.

Astronomers have discovered 12 additional moons in orbit around Jupiter, bringing the total to 79, the most of any planet in the solar system, a new study found.

The moons were discovered while astronomers were searching for objects at the edge of the solar system, according to Scott Sheppard, a scientist at the Carnegie Institution for Science who co-authored the study.

“Jupiter just happened to be in the sky near the search fields where we were looking for extremely distant solar system objects, so we were serendipitously able to look for new moons around Jupiter while at the same time looking for planets at the fringes of our solar system,” Sheppard said.

One of the objects they were looking for is the mysterious "Planet X" or "Planet Nine," which remains undiscovered.

The discovery of the new moons was reported Tuesday in the Minor Planet Electronic Circular, a publication of the International Astronomical Union.

Researchers say the new Jupiter moons weren’t seen before because they are tiny – the biggest ones are only about two miles across.

One of the newly discovered moons is an "oddball," Sheppard said. "It has an orbit like no other known Jovian moon,” he explained. It orbits in an opposite direction from the other moons near it, meaning head-on collisions are much more likely to occur.

“This is an unstable situation,” said Sheppard. “Head-on collisions would quickly break apart and grind the objects down to dust.

“It’s also likely Jupiter’s smallest known moon, being less than one kilometer (0.6 mile) in diameter."

Telescopes in Chile, Hawaii and Arizona were used for the original discovery and year-long confirmation of the moons.

“It takes several observations to confirm an object actually orbits around Jupiter,” said Gareth Williams of the International Astronomical Union’s Minor Planet Center. “So, the whole process took a year.”
Two of Jupiter's moons, S/2003 J 18 and S/2011 J 2 are recovered, and a small 1.5-kilometer outer moon (S/2016 J 1) is discovered, the first moon discovered around a major planet in 6 years.