Astronomers Have Discovered a Dozen New Moons Circling Jupiter

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Jupiter's neighborhood was always crowded, but the discovery of 12 new moons around the giant planet makes it more intriguing.

The latest discovery of a dozen small moons brings the total to 79, the most of any planet in our solar system.

Once the Blanco telescope spotted previously unidentified objects near Jupiter, the research team used other telescopes to follow up on these moon candidates and confirm that they were orbiting Jupiter.

Astrophysicists believe that these small moons, which are clustered in three bands, are the remnants of three massive moons which were broken apart by collisions with other bodies in space.

Two of the new moons orbit Jupiter closer in, and are prograde. Many of Jupiter's outer moons were likely formed by collisions between larger retrograde moons and oddball prograde satellites. "Head-on collisions would quickly break apart and grind the objects down to dust". Nearly all of Jupiter's prograde moons are believed to be fragments of a larger moon that broke apart. After their observations and more than a year of follow-ups and confirmations, they announced this week that they found 12 new moons. Because it's moving in the opposite direction of the other moons, a head-on collision is much more likely.

Gareth Williams, an astronomer at the Harvard-Smithsonian Center for Astrophysics and director at the International Astronomical Union's Minor Planet Center, predicted that "there aren't any bigger objects undiscovered out there" around Jupiter.

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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. When Jupiter and the other giant planets were forming, the solar system was a disk and gas and dust that surrounded the infant Sun. The 7 new retrograde moons join 45 other satellites that take 2-3 years to orbit.

Scientists classified the findings as 11 "normal" outer moons, and another that they are calling an "oddball" for its unusual orbit.

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. But Valetudo, in addition to being the smallest discovered, orbits in prograde, or the same direction as the planet's spin.

It is possible the various orbital moon groupings we see today were formed in the distant past through this exact mechanism. Sheppard's girlfriend came up with a name for it: Valetudo, the great-granddaughter of the Roman god Jupiter. Of the twelve, only three moons orbit in a prograde direction, and are closer to Jupiter. The discovery is thanks to a team led by Scott Sheppard of the Carnegie Institution for Science who first noticed the moons in Spring 2017. Nine of them have retrograde orbits, going in the opposite direction to Jupiter's spin.

Valetudo is more distant and more inclined than the prograde group of moons and takes about 1.5 years to orbit Jupiter. Maybe we need something similar for tiny moons.

Over the weeks following full opposition, Jupiter will reach its highest point in the sky four minutes earlier each night, appearing as a bright, star-like object.

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