A dozen new moons orbiting Jupiter have been discovered by astronomers... by mistake. This tells us something about the timing of the formation of these moon families, which, in turn, tells us something new about the formation of the Solar System.
Jupiter's moons range in size from shrimpy satellites to whopping space hulks.
Even better, they were found as a kind of bonus.
They were hunting a possible massive planet beyond Pluto when they stumbled upon the mysterious satellites - one of which has been described as an "oddball". They also are thought to be the result of an earlier collision and take about a year to complete one orbit. Because it's like peering around the trees in our own forest and trying to count them all rather than using an overhead drone, Sheppard said.
Valetudo, as spotted through the Magellan telescope in May 2018. Jupiter is not in the frame and is off to the upper left. "It's like it's going down the highway in the wrong direction".
The "oddball" moon, which has been named Valetudo after the Roman goddess of health and hygiene, has an orbit that is dissimilar to any other known moon around Jupiter.
The Minor Planet Center published the remaining 10-pack's orbital parameters today, marking their formal acceptance as Jovian moons. So, unlike the closer-in prograde group of moons, this new oddball prograde moon has an orbit that crosses the outer retrograde moons.
Also, if the moons had formed earlier, there likely would have been more crashes, the team explained.
Because it's orbiting in the opposite direction of the nine "new" retrograde moons, and across their paths, there is a high risk that it will hit one of them, according to the statement.
Astronomers suspect that the retrograde moons may be the remains of larger moons that were destroyed in head-on collisions with prograde objects. This unusual orbit makes it prone to collisions with the retrograde moons that are moving in the opposite direction. Astronomers believe they were once all part of a larger moon that broke apart. This is in contrast to other Jupiter moons such as Ganymede - the biggest in the solar system with a diameter of 5,268km. Nine of these moons are from a previously discovered cluster of moons that are in what astronomers call a retrograde orbit. "Magnificent desolation", Sheppard says, is the ideal.
The giant planet region is where the largest planets in our solar system formed, and it's devoid of objects now because the planets gobbled up all of the material to form.
Jupiter's moons are arranged in a specific pattern that the giant planet has worked out over time. Maybe we need something similar for tiny moons. If small moons like these were around when the solar system was still thick with gas and dust, drag forces would have slowed them down and caused them to fall into Jupiter, never to be seen again.
The last of the team's discoveries is the strangest of them all. "It reminds me that always searching the question of "what is out" is an unfolding".