Discovered 12 new moons of Jupiter (and there are already 92)

The astronomer Rafael Bachiller reveals to us in this series the most spectacular phenomena of the Cosmos.

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The discovery of 12 new moons orbiting Jupiter brings the number of known satellites in the king of planets to 92.

The Jupiter family therefore exceeds that of Saturn, which has 83 cataloged moons.

record planet

Jupiter breaks many of the records in the solar system.

With a mass greater than 318 times that of Earth and a volume 1,320 times greater, it is the most massive and the most voluminous of our planetary system.

In its permanently cloud-covered atmosphere is the largest meteorological formation in the solar system: the Great Red Spot, a gigantic anticyclone whose surface area is 15 times greater than that of our Earth's disk.

Now Jupiter has just broken another record: its family of moons already has 92 members, thus surpassing that of Saturn, made up of 83 known satellites.

Confirmation of the 12 Jovian moons found in recent observations has been made by the Minor Planet Center (MPC) of the International Astronomical Union.

The observations have been made and analyzed by astronomer Scott Sheppard of the Carnegie Institute for Science (Washington, USA.).

progrades and retrogrades

All of these new moons are small (one to two kilometers in size) and orbit far from Jupiter, their orbital periods are between 430 and 740 days.

Some of Jupiter's moon clustersCarnegie Inst./S.

Sheppard

The three least distant moons of the 12 newly discovered move with prograde or direct orbits.

That is, they are moons whose rotation movement goes counterclockwise, seen from the solar North Pole, the same direction of rotation that presents the orbit of Jupiter itself and previously known interior moons.

These moons are thought to have formed in the same place they are now, next to the gas giant.

Paradoxically, these moons are the most difficult to identify, since the glow of the planet makes it difficult to observe in their vicinity.

The other nine new moons are very external and are part of the groups that orbit with a retrograde movement (in the opposite direction to the rotation of the planet and the inner moons).

This movement indicates that they did not form with the giant planet, but rather were captured by it throughout its lifetime.

Very possibly the smaller moons are the result of fragmentation, through collisions, of larger objects.

Jovian moons in groups

Jupiter's moons can be classified into several groups.

In order of distance, as we move away from the planet, we first encounter the prograde moons.

The innermost group is made up of 4 small satellites that orbit less than 250,000 kilometers from Jupiter.

Due to the difficulty of observing so close to the planet, these moons were not discovered until 1975.

Next, we have the most popular group, that of the four Galilean moons, so named because they were discovered by Galileo with his rudimentary telescope.

The members of this group -Io, Europa, Ganymede and Callisto- are the most massive in the Jovian system, orbiting at distances between 0.4 and 1.9 million kilometers from Jupiter.

Next comes Themisto, much further away, which rotates alone 7.4 million kilometers from Jupiter and does not seem to be part of any known group.

Next are the nine moons in the Himalia group that orbit between 11 and 12 million km from Jupiter and, a little further out, the pair of moons Carpus, at 17 million km.

Then comes another lonely and small moon (1 km in size), Valetudo.

At 19 million from Jupiter, this is the most distant of the known prograde moons.

Polar view of some groups of Jupiter's moonsCarnegie Inst./S.

Sheppard

Valetudo is a somewhat exceptional moon, since its orbit is already located between the three groups of retrograde moons, which are the outermost (Ananke, Carme and Pasiphae).

It is not impossible that, over time, Valetudo collided head-on with one of those retrograde moons, thus causing its fragmentation.

Difficult task

Identifying new moons in the giant planets, and calculating their orbits, is a complex task.

It requires more effort than doing the same job for asteroids and comets.

The orbits of the latter are only determined by the solar attraction, while for the moons it is necessary to take into account the effect of both their planet and that of the Sun.

In addition, to unambiguously conclude that we are observing a moon, it is necessary to follow its complete orbit, which, as we have seen, can require several years for the smallest satellites.

distant.

That is why, although these new moons were sighted between 2016 and 2021, their confirmation could not be made by the MPC until very recently.

Scott Sheppard's post can be found at this link [https://bit.ly/3kXrQA3].

Rafael Bachiller is director of

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