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. Jupiter, the largest planet in the solar system, was hardly short of moons before the latest findings. One of a dozen new moons discovered around Jupiter is circling the planet on a suicide orbit that will inevitably lead to its violent destruction, astronomers say. Astronomers have discovered a dozen new moons orbiting Jupiter, but one could spell disaster for the others - 1km-wide "oddball" moving in the opposite direction to the other 78 objects circling the gas giant.A team led by Scott S. Sheppard from Washington DC's Carnegie Institution for Science first spotted the moons in 2017 while on the hunt for a possible massive planet beyond Pluto. “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. Thus head-on collisions are likely.”



Sheppard, whose report appears in the International Astronomical Union Minor Planet Electronic Circular, suspects that Valetudo is the final remnant of a once much larger moon that has been ground to dust by collisions in the past. Researchers say the new Jupiter moons weren’t seen before because they are tiny – the biggest ones are only about two miles across. The team is calling one of the new moons an ‘oddball’ because of its unusual orbit. The fresh haul of natural satellites brings the total number of Jovian moons to 79, more than are known to circle any other planet in our cosmic neighbourhood. Nine of the new moons belong to an outer group that orbit Jupiter in retrograde, meaning they travel in the opposite direction to the planet’s spin. “What astonishes me about these moons is that they’re the remnants of what the planet formed from,” he said. “Head-on collisions would quickly break apart and grind the objects down to dust. Two more of the moons are in a group that circle much closer to the planet in prograde orbits which travel in the same direction as Jupiter’s spin. Telescopes in Chile, Hawaii and Arizona were used for the original discovery and year-long confirmation of the moons. "The team at the Carnegie Institution think that the oddball moon - potentially to be named Valetudo, after the Roman god Jupiter's great-granddaughter - may represent the leftovers of a former larger moon.Gareth Williams at the International Astronomical Union's Minor Planet Center used the team's observations to calculate orbits for the newly-found moons. “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.
Astronomers discover a giant gaseous planet orbiting a pair of brown dwarfs.