Jupiter Quietly Takes Crown for Most Moons, With New Tally of 92

We only have one Moon, very big, true, but there are planets that already have close to 100 satellites…

The International Astronomical Union has officially approved the existence of 12 new moons of Jupiter. The largest planet in the Solar System already has 92 moons.

It thus surpasses Saturn, which until now had a record of 83 satellites. Astronomers are convinced that both planets have more, and some of them will even exceed 100 moons in a short time.

Its discoverer, astronomer Scott Sheppard, already discovered 12 other Jupiter moons in 2018. He has become an expert in this matter, since he has also found moons of Saturn, Uranus and Neptune.

Jupiter’s first moon was casually cited by the Chinese astronomer Gan De, in the year 364 BC. But it was Galileo Galilei who described the orbits of the four largest, Ganymede, Io, Callisto and Europa, in 1610.

Jupiter’s new moons
If Jupiter’s satellites were already known centuries ago… why are we discovering so many now? The reason is that the new moons are very small, between 1 and 10 kilometers in diameter, and are very difficult to see. You may not know it, but Earth also has a second tiny moon.

Satellites do not emit light like stars or reflect as much light as planets. In the case of Jupiter, it reflects so much light that it literally blinds telescopes when looking for small moons orbiting nearby.

The 12 new moons of Jupiter do not have a name, only a numbering, because as we say they are very small. Most are less than 8 kilometers in diameter. Scott Sheppard believes that they are fragments of larger moons that collided with each other, or with a meteorite.

As Sky & Telescope explains, nine of these moons trace outer orbits in retrograde motion, that is, in the opposite direction to Jupiter’s (closest) inner moons. Their orbits take up to 550 days to go around the planet, compared to approximately 28 days for our Moon.

Two other moons orbit in what they call the Himalia group, at a distance of about 11 million kilometers from Jupiter. The last satellite is in the Carpo group, about 17 million kilometers from the planet.

Here you can see some of Jupiter’s moons, and how they rotate. New ones are not included:

Surely the green orbit of the moon Valetudo has caught your attention. It was discovered by Sheppard in 2018, and it is a suicide moon: it goes in the opposite direction to the other outer moons. Sooner or later it will be attracted to something bigger, and it will end up crashing into it.

Jupiter has 12 new moons and already has 92 satellites, surpassing Saturn as the planet with the most moons in the Solar System. The race is not over. Astronomers are convinced that they will discover more satellites on both planets.