The Hunt for 'Planet Nine' Discovers 12 New Moons Around Jupiter

The Hunt for 'Planet Nine' Discovers 12 New Moons Around Jupiter

The Hunt for 'Planet Nine' Discovers 12 New Moons Around Jupiter

Which direction the moons swing around the planet depends on how they were first captured by Jupiter's gravitational field. The nine moons are thought to be the fragments of three larger bodies that collided with asteroids, comets or other moons.

The other nine moons, grouped in clusters of three, have retrograde orbits.

That brings the number of moons at Jupiter to 79, the most of any planet. It has an orbit like no other known Jovian moon. Valetudo is the name of Jupiter's great-granddaughter and a Roman goddess of health and hygiene, so it fits the bill.

Europa is believed to have a vast liquid ocean beneath its icy surface and is among the likely habitable places in the Solar System beyond our own Earth. For example, as Jupiter orbited the newborn sun, it likely carved a gap in the protoplanetary disk of gas and dust that surrounded the infant star, limiting the amount of solid matter that could have spiraled from the outer solar system into the inner solar system to form the planets there.

The newfound moons are small, between about 1 and 3 kilometers across.

Based on the team's observations, Gareth Williams at the International Astronomical Union's Minor Planet Center was able to calculate the orbits of the moons.

Jupiter's moons are arranged in a specific pattern that the giant planet has worked out over time. Many of Jupiter's outer moons were likely formed by collisions between larger retrograde moons and oddball prograde satellites.


Nine of the new moons are in the retrograde group, a distant bunch of moons that rotate in the opposite direction of Juipter.

"This is an unstable situation", said U.S. astronomer Dr Scott Sheppard from the Carnegie Institution for Science in Washington DC, who led the discovery team. It orbits Jupiter in and amongst where the retrograde moons reside, however, it follows a highly risky prograde orbit as it does so.

One moon in particular caught the researchers' attention.

The team was using the Blanco 4-metre telescope at Cerro Tololo Inter-American Observatory in Chile, which recently got upgraded with the Dark Energy Camera. In 2017, the group reported two additional Jovian moons. Two of the 12, on the other hand, are found in a closer group that orbits Jupiter in prograde, which is the same direction of the planet's rotation.

It's possible the various orbital moon groupings we see today were formed in the distant past through this exact mechanism. Sheppard's team speculates Valetudo could be a remnant of a collision between one or more moons.

The team's results are not yet available in a peer-reviewed journal, as Sheppard's team is now running supercomputer simulations to try and figure out how often Valetudo might collide with a retrograde moon.

Sheppard and his colleagues speculate that Valetudo was probably once much larger, but was ground down, over the course of billions of years, as a result of collisions. Maybe we need something similar for tiny moons. Jupiter's strong gravity may also have disrupted the orbits of nascent planets, potentially even hurling them into interstellar space. That makes it a powerful tool for surveying the night sky in search of faint objects.

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