Published: Wed, July 18, 2018
Sci-tech | By Jackie Newman

Jupiter's moon count reaches 79, including tiny 'oddball'

Jupiter's moon count reaches 79, including tiny 'oddball'

Astronomers searching for a planet beyond Pluto discovered instead a dozen new moons orbiting Jupiter.

They said the space rocks were created when three larger bodies that once orbited the planet were obliterated into smaller chunks by collisions with asteroids. Which direction the moons swing around the planet depends on how they were first captured by Jupiter's gravitational field.

The announcement of the new moons was published Tuesday in the International Astronomical Union Minor Planet Electronic Circular.

It's easy to understand why these 12 new additions had been missed so far. It may sound chaotic, but since "they're at different distances, they don't really ever interact with one another", Sheppard says.

Using the Blanco four-metre telescope at Cerro Tololo Inter-American in Chile - which had been recently fitted with a new and highly sensitive instrument called the "Dark Energy Camera", which is about the size of a small vehicle - they detected objects that seemed to be moving against the background stars.

To check whether this could have happened, the researchers are working on supercomputer simulations of these orbits to calculate how many times an object with Valetudo's orbit could have collided with the retrograde moons in the solar system's lifetime.

This isn't likely to be the last new moons that we hear about coming from the gas giant, and astronomers believe there are still plenty smaller satellites that remain undetected.

This new "oddball" moon is more distant and more inclined than the prograde group of moons and takes about one and a half years to orbit Jupiter.

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Nine of the new moons belong to an outer group that orbit Jupiter in retrograde, meaning they travel in the opposite direction to the planet's spin.

This April 2017 image shows the planet Jupiter.

Closest to the planet are the four small "inner irregulars", named Metis, Adrastea, Amalthea and Thebe. The Galilean moons - Ganymede, Io, Callisto and Europa - are the largest and can be seen from Earth using binoculars. Each takes about two years to circle the planet.

Researchers would like to get a close-up look at the moons.

Most moons, including Earth's, have prograde orbits. Several telescopes were used to confirm the finds, including the 6.5-meter Magellan telescope at Carnegie's Las Campanas Observatory in Chile; the 4-meter Discovery Channel Telescope at Lowell Observatory Arizona (thanks to Audrey Thirouin, Nick Moskovitz and Maxime Devogele); the 8-meter Subaru Telescope and the Univserity of Hawaii 2.2 meter telescope (thanks to Dave Tholen and Dora Fohring at the University of Hawaii); and 8-meter Gemini Telescope in Hawaii (thanks to Director's Discretionary Time to recover Valetudo). TheyÂre calling one moon an ‘oddball because of its unusual orbit.

Sheppard said Jupiter and Saturn may actually have a similar number of moons, with some of the latter's smaller ones not yet detected. Sheppard's girlfriend came up with a name for it: Valetudo, the great-granddaughter of the Roman god Jupiter. These satellites are part of a large group of moons that orbit in retrograde far from Jupiter.

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. The outer moons move in the opposite direction - a retrograde orbit. The moon's 1.5-year orbit is also more oblong, which means the moon cross paths with the outer retrograde moons.

"Jupiter is like a big vacuum cleaner because it's so massive", Sheppard said.

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