Astronomers discover "12 more moons" for Jupiter, making it the "King of the Moons".

The king of planets Jupiter is now also the king of moons, at least for now, due to the discovery of a dozen new moons for Jupiter.  Jupiter has replaced Saturn as the new "Moon Master" of the solar system. 

Due to the discovery of 12 newfound satellites, Jupiter currently has more moons than Saturn.  Jupiter has surpassed Saturn as the "solar system planet with the most moons" with these new discoveries. 

According to a new report from Sky and Telescope, the Minor Planet Center (MPC) has published the orbits of the 12 hitherto undiscovered moons of Jupiter.

The planet's known moons have increased by 15% as a result of the dozen new moons.  The new discoveries raise the number of Jovian moons from 80 to 92, a significant 15% increase. 

All of the 12 newly discovered moons are small and far out, taking more than 340 days to orbit Jupiter.  Only five moons have a diameter larger than 8 kilometers (5 miles).

Of the 12 new moons, nine are particularly distant. Nine of the 12 are among the 71 outermost Jovian moons, whose orbits are more than 550 days.

Discovering New Moons

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Minor Planet Center Electronic Circulars typically report the discovery of small moons of Jupiter or Saturn. These reports, however, take time.

It is more difficult to analyze observations and determine trajectories for planetary moons than for asteroids or comets since a moon’s path depends on both the gravity of its planet as well as the Sun.

Observations must also monitor the moon for a full orbit to prove it truly orbits the planet, and Jupiter's outer moons take around two years to orbit the planet. 

To show that it actually orbits the planet, and Jupiter's outer moons take about two years to orbit the planet, the observations must track the moon for a complete orbit.

On the other hand, the path of comets and asteroids depends only on the Sun, therefore a few weeks of observations may suffice to predict their course.

Because Sheppard, Gladman, and other researchers continue their search for new moons in the outer solar system, we can expect more reports.

This diagram shows the orbits of moons around Jupiter: Purple denotes the Galilean moons, yellow for Themisto, blue for the Himalia group, cyan and green for Carpo and Valetudo, respectively, and red for far-out retrograde moons. (Note: The number of moons in this diagram is not up to date.) - Scott Sheppard

This diagram helps visualize the grouping of moons by their orbits: The Galilean moons are the innermost and most massive moons (purple). The planet's prograde moons (purple, blue) orbit relatively close to Jupiter while its retrograde moons (red) are farther out. One exceptions is Valetudo (green), a prograde-moving body that's far out. - Carnegie Inst. for Science / Roberto Molar Candanosa