Astronomers Just Announced The Discovery of 12 New Moons Around Jupiter

The moons are small, ranging from just one kilometre to three kilometres in width.

Sheppard, who led the team, said Jupiter just happened to be in the sky near the search fields where they were looking for extremely distant solar system objects so they were serendipitously able to look for new moons around Jupiter at the same time. One moon detected by Sheppard and his colleagues is the smallest Jovian moon ever discovered. Valetudo is the name of Jupiter's great-granddaughter and a Roman goddess of health and hygiene, so it fits the bill.

Many prior studies have suggested that Jupiter has greatly influenced the evolution of the solar system. This putative planet is now sometimes popularly called Planet X or Planet Nine.

"Our solar system is odd for not hosting a super-Earth, since it's the most common type of planet, and now we find that it's also odd for not having a super-Earth despite having a Jupiter", Bryan said.

Two of the newly discovered satellites orbit with a group that are in between the outer group and the Galilean moons.

Gareth Williams at the International Astronomical Union's Minor Planet Center used the team's observations to calculate orbits for the newly found moons. That means the revolve around Jupiter opposite from the planet's rotation.

The renegade moon has an inclined orbit that crosses those of others moving in the opposite direction, greatly increasing the possibility of a collision. Additional observations over a year confirmed the orbits of the moons, all of which are 3 kilometers or less in diameter. The oddball also orbits in prograde, but at a greater distance than the other prograde moons. Not yet, anyway. "Right now the only definition of a moon is something that orbits the planet", Sheppard said, as long as it isn't human-made.

Also, if the moons had formed earlier, there likely would have been more crashes, the team explained.

The moons are remnants of what was out there, born in the disc of gas and dust around Jupiter after the planet formed and then captured and pulled into Jupiter's orbit. The retrograde set of moons take about two years to complete a lap around Jupiter, and the prograde ones take under a year.

This screencapture shows the prograde moons of Jupiter, including the two newest discoveries. "Most of the small objects that helped build the planets we see today were incorporated into the planets themselves, and these moons are all that remains", Sheppard wrote.

That seems to be what happened to astronomers working at the Cerro Tololo Inter-American Observatory in Chile, where a planned survey of trans-neptunian objects was interrupted by Jupiter.

The team believes Valetudo might be a fragment of a larger moon, broken off in a collision with a larger retrograde moon, resulting in something like the retrograde groupings observed. The orbits of the new moons are marked with thicker curves.

In fact, Sheppard and his team at Carnegie think that this moon could be all that's left of a previous collision in orbit around Jupiter. "Maybe there will have to be a new definition for the smaller moons". That makes it a powerful tool for surveying the night sky in search of faint objects.

  • Joey Payne