A dozen new moons have been discovered orbiting Jupiter.
The new finding brings the total number of moons around the gas giant to a whopping 79 – the most of any planet in the solar system.
Astronomers accidentally spotted the tiny satellites while searching for a possible massive planet beyond pluto known as Planet X.
They said the space rocks were created when three larger bodies that once orbited the planet were obliterated into smaller chunks by collisions with asteroids.
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Three groupings of Jupiter’s moons with a dozen newly discovered ones shown in bold. One of the satellites, called Valetudo (green), has a unique orbit that means it spins in the opposite direction to the others, putting it at risk of a catastrophic collision
The researchers, from the Carnegie Institution for Science in Washington, DC, picked out one of the 12 moons as an ‘oddball’.
The so-called ‘oddball’ has such a unique orbit that it is at risk of smashing into the other moons – a cosmic collision that could risk wiping the space rocks out.
Team leader Dr Scott Sheppard said: ‘It’s a real oddball. It has an orbit like no other known Jovian moon. It is also likely Jupiter’s smallest known moon, being less than one kilometre [0.6 miles] in diameter.’
The team discovered 12 new Jovian moons, ten of which were never-before-seen objects, while a further two had been spotted previously by scientists.
The chance find brings the gas giant’s tally of moons to 79 – 17 more than Saturn, the planet with the second most orbiting moons in the solar system.
At less than two miles (3.2km) wide, the moons are all very small, which is why they have only now been identified thanks to the team’s modern, sensitive telescopes.
Eleven are ‘normal’ moons, with nine of them part of a distant outer swarm that orbit in the retrograde, meaning they move in the opposite direction to Jupiter’s spin.
They are thought to be the remnants of three once larger moons that broke apart during collisions with asteroids, comets or other moons.
They take about two years to orbit Jupiter, which is the largest planet in the solar system.
The remaining two satellites others are among a closer, inner group that orbit in the prograde, or same direction.
They are also believed to be fragments of a larger moon that was broken apart and take just under a year to circle Jupiter.
Astronomers spotted the new moons while looking for a possible massive planet beyond Pluto. One of the moons, Valetudo (between orange markers), can be seen in these images. Jupiter is out of view, off to the upper left
It’s further away than the prograde moons, taking around one and a half years to orbit around the planet.
This means, unlike those closer to Jupiter, it crosses the outer retrograde moons.
As a result, head on collisions are much more likely to occur between this ‘oddball’ prograde moon and its retrograde cousins moving in opposite directions.
Dr Sheppard said: ‘This is an unstable situation. Head-on collisions would quickly break apart and grind the objects down to dust.’
It is possible the various orbital moon groupings we see today were formed in the distant past through this exact mechanism.
The chance find brings Jupiter’s tally of moons to 79, 17 more than Saturn, the planet with the second most. This image of Jupiter was taken by Nasa’s Juno probe last year
The team suspect the ‘oddball’ is the last-remaining remnant of a once-larger prograde moon that formed some of the retrogrades during past head-on collisions.
The name Valetudo has been proposed for it, after the Roman god Jupiter’s great-granddaughter, the goddess of health and hygiene.
The initial discovery of most of the new moons were made on the Blanco 4-meter telescope at Cerro Tololo Inter-American in Chile and operated by the National Optical Astronomical Observatory of the United States.
Several other telescopes were used to confirm the finds, including the 6.5-meter Magellan telescope at Carnegie’s Las Campanas Observatory, also in Chile.
Elucidating the complex influences that shaped a moon’s orbital history can teach scientists about our solar system’s early years.
WHAT IS JUPITER’S OPPOSITION AND WHEN IS THE BEST TIME TO VIEW THE PLANET IN 2018?
The effect of opposition is similar to the effect of the full moon seen once a month when Earth is positioned directly between our natural satellite and the sun.
This orbital arrangement means Jupiter appears as the largest disc in the sky and will be visible from sundown to sunrise.
While the planet was visible to the naked eye during its peak opposition on May 8, for the next few weeks star-gazers should be able to spot it through binoculars or a telescope.
The effect of opposition is similar to the effect of the full moon seen once a month when Earth is positioned directly between our natural satellite and the sun
During its full opposition the planet was brightest in Britain on May between 9:30pm and 4:30am BST while in the US it peaked on May 9 between 1:10am and 6:20am ET.
Over the weeks following full opposition, Jupiter will reach its highest point in the sky four minutes earlier each night, appearing as a bright, star-like object.
It will appear as the fourth brightest object in the sky behind the moon, Mars and Venus.
For example, the discovery that the smallest moons in Jupiter’s various orbital groups are still abundant suggests the collisions that created them occurred after the era of planet formation.
This was at a time when the Sun was still surrounded by a rotating disc of gas and dust from which the planets were born.
Due to their sizes – just 0.6 to 1.9 miles (1 to 3km) in diameter – these moons are more influenced by surrounding gas and dust.
If these raw materials had still been present when Jupiter’s first moons collided to form its current clusters, the drag exerted on the smaller ones would have made them spiral inwards. So they were likely formed after they had dissipated.