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Ten moons were discovered in orbit around Jupiter – 9 "normal" outer and a "ball" – scientists from the Carnegie Institution for Science in Washington reported Tuesday.
Including the previously unknown moons, Jupiter now has 79 known moons in orbit around the giant planet, more than any other planet in our solar system. Saturn has the second largest number of known moons: 61.
The team of scientists, led by Scott Sheppard, identified the moons in March 2017 accidentally, while they were looking for small, far-off objects at the periphery of the solar system – including a planet possibly- to be massive well beyond Pluto.
"Jupiter was right in the sky near the search fields where we were looking for extremely distant Solar System objects, so we were able to search for new moons around Jupiter while searching for planets at the margins of our solar system. Sheppard said in a statement released by Carnegie.
The confirmation of 10 moons was announced Tuesday; two were confirmed in June 2017. Scientists say the moons had not been seen before because they are tiny – the largest only about two miles in diameter.
"It takes several observations to confirm that an object is actually revolving around Jupiter," said Gareth Williams of the Planet Minor Minor Center of the International Astronomical Union. "So, the whole process took a year." Telescopes in Chile, Hawaii and Arizona were used for discovery and confirmation.
Sheppard tells Haaretz that astronomers were studying the sky near Jupiter and because Jupiter's orbital velocity is known, anything that comes close to him at a similar speed and which was not known became a new Moon. They re-examined the candidates a month later, and then a year later, to make sure that they were really orbiting Jupiter, Sheppard said.
The area near Jupiter that could contain moons is much larger than the area that telescopes can see and it takes a long time to study this area, so it's safe to assume that more moons to discover, said Sheppard.
Nine of the new moons are part of a distant outer swarm of moons that orbit it in retrograde rotation, or the opposite direction of Jupiter's rotation, Carnegie said. These distant retrograde moons are grouped into at least three distinct orbital clusters and are considered to be the remains of three formerly larger parent bodies that separated in collisions with asteroids, comets, or other moons. The newly discovered retrograde moons take about two years to orient Jupiter.
Two other moons are part of an inner group closer to moons that rotate in the same direction as the rotation of the big planet. These inner moons all have orbital distances and similar tilt angles around Jupiter and are also considered fragments of a larger moon that has broken. These two newly discovered moons take a little less than a year to steer Jupiter.
"Our other discovery is a real nonsense and has an orbit like no other known jovian moon," Sheppard said. "It is probably the smallest known moon of Jupiter, having less than one kilometer in diameter".
This "weird" moon moves in the same direction as Jupiter but is larger than the others and takes about a year and a half to orbit the planet. This single orbit brings the new moon far enough so that a frontal collision is more likely to occur between the "offset" moons and the retrograde moons, which move in opposite directions.
"It's an unstable situation," Sheppard said. "The frontal collisions would break quickly and reduce the objects to dust."
It is possible that such collisions are what formed the moons we see today and the strange moon is the last vestige of a larger moon that collided with these other moons. and led to the creation of the retrograde moons of today. These moons are perhaps the only remnants of the original materials of the planets and their understanding could help to understand how the planets were created, adds Sheppard.
>> Birth of a planet photographed for the first time, giving a glimpse of the early childhood of the solar system >>
The name Valetudo was proposed for this larger moon, according to the great-granddaughter of the Roman god Jupiter, the goddess of health and hygiene.
Prof. Oded Aharonson, director of the Planetary Science Center at the Weizmann Institute of Science in Rehovot, said that the importance of discovery does not lie in the exact number of moons found, but in the new light on two questions at the heart of contemporaneity. study of the solar system. The first is the influence of collisions between objects in the planetary gravitational field on the formation of the solar system as we know it today.
The second glimpse of research on Jupiter's new moons, and particularly the weird moon, is that our solar system is dynamic – and still is today, says Aharonson. The solar system did not freeze 4.5 billion years ago, things are still changing.
Moons are born again and collide. In theory, it is possible to calculate when the next collision will occur, if it will happen soon, he says. But the most interesting calculation, according to Aharonson, is to compare the Jupiter system to that of other similar planetary systems and to calculate the average lifespan of these moons – and to better understand the story of Jupiter. and his moons.
In 2014, the same team of scientists found the object with the most distant known orbit in the Solar System and was the first to realize that a massive unknown planet at the limits of our Solar System, well beyond Pluto, could explain the similarity of the orbits of several extremely distant small objects. This putative planet is often popularly called Planet X or Planet Nine.
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