Astronomers discover 12 more moons of Jupiter, including a curiosity



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  These images show the movement of the moon of Jupiter nicknamed Valetudo (marked in yellow) compared to the background stars

These images show the movement of the moon of Jupiter called Valetudo (marked in yellow) compared to the stars background. : NASA

"We were able to go a little lower than anyone else could in the past," said Sheppard, "and that's why we were able to find these new moons. "

Jupiter's moons range from the size of shrimp satellites to huge carcasses of space. Galileo discovered the first four moons of Jupiter, all enormous, in 1610. The largest Galilean moon, Ganymede, is larger than the planet Mercury. These moons are in orbit around Jupiter and travel in the same direction as the planets.

The moons Sheppard saw are smaller and smaller, each a little over three kilometers in diameter. A moon detected by Sheppard and his colleagues is the smallest Jovian moon ever discovered. They called Valetudo, after a daughter of Jupiter and the Roman goddess of hygiene and personal health.

Gareth Williams, astronomer at the Harvard-Smithsonian Center for Astrophysics and director of the Minor Planet Center of the International Astronomical Union, predicted that around Jupiter, there is no such thing. Larger objects not discovered.

But he said that he expected astronomers to discover more tiny moons in the coming decades. Regarding the number of satellites orbiting Jupiter, Williams fears "to think of the number of objects in the range of 100 meters."

  An image of the moon of Jupiter Europa, with the giant planet background. An image of NASA from the moon of Jupiter Europa, with the giant planet in the background. </p>
<p><cite>  Photo: <!-- --> NASA </cite></figcaption></figure>
<p>  Size is not a condition for being a moon – there is no dwarf moon. Not yet anyway. "Currently, the only definition of the moon is something that orbits the planet," says Sheppard, as long as it's not human. </p>
<p>  Astronomers group the moons of Jupiter by their distance to the planet and their orbital direction. If a moon rotates in the same direction as the rotation of a planet, the orbit of this moon is called prograde. If the moon rotates around a planet in the opposite direction of a rotating planet, this orbit is retrograde. (A small subset of the 79 moons of Jupiter do not have well-known orbits.) </p>
<p>  Most moons, including those of the Earth, have prograde orbits. Two of the newly discovered moons, the closest to Jupiter, also have prograde orbits </p>
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The other nine moons, grouped in groups of three, have retrograde orbits. These moons were probably part of much larger moons that have fragmented into smaller objects, Sheppard said. Astronomers perform computer simulations to determine how ancient moons have fragmented.

  This composite includes the four largest moons of Jupiter known as Galilean satellites. The Galilean satellites were first seen by the Italian astronomer Galileo Galilei in 1610. From left to right in the increasing order of distance from Jupiter, Io is the closest, followed by Europa, Ganymede and Callisto. of Jupiter who are known as the Galilean satellites. The Galilean satellites were first sighted by the Italian astronomer Galileo Galilei in 1610. From left to right in the increasing order of distance from Jupiter, Io is the closest, followed by Europa, Ganymede and Callisto </p>
<p><cite>. 19659004] Valetudo is something weird. It has a prograde orbit at a distance where the rest of Jupiter's moons have retrograde orbits. Moreover, these orbits intersect. In other words, the scene is defined for possible moon-moon collisions. </p>
<p>  Astronomers do not know the composition of the dozen newly identified moons. They could be rock, ice or a mixture. "The only thing we know for now are the orbits and the approximate size," Williams said. "We know nothing, really, more than that." </p>
<p>  The kingdom of giant planets – between Jupiter, Saturn, Uranus and Neptune – is largely devoid of small objects. When these planets were formed, their gravity sucked nearby gases, rocks, and other debris. This case became part of the planets themselves </p>
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But Sheppard suspects that these moons might be delays, the "last vestiges" of first objects of the solar system. "Looking at these outer moons," he says, "we can get an idea of ​​what were the objects that ended up forming the planets we see today."

The Washington Post

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