A team of astronomers reported the recent discovery of a dozen new moons circling the giant gas planet. The scientists embarked on a yearlong process that involved several observations to confirm the moons' existence, according to a Carnegie Institution for Science press release.
Most of the new moons were revealed by the Blanco 4-meter telescope at Cerro Tololo Inter-American, located in Chile, which was recently outfitted with a Dark Energy Camera created to locate faint objects.
Two of the new moons are part of the prograde group, a bunch of moons that are relatively close to Jupiter and rotate in the same direction as the planet. The newly discovered retrograde moons take about two years to orbit Jupiter.
They also have a retrograde orbit, or the opposite direction to the spin of Jupiter on its axis. The irregular satellites didn't form around Jupiter in the same way that the planets formed around the Sun, or the regular satellites around Jupiter, from a flat disc in a prograde orbit.
"Our other discovery is a real oddball and has an orbit like no other known Jovian moon", said Scott Sheppard, lead scientist on the project and a staff scientist at the Department of Terrestrial Magnetism in Washington, D. C.
The oddball is thought to be Jupiter's smallest moon; it measures roughly 3,000 feet across.
Astronomers peering into the depths of the solar system in search of a presumed ninth planet far beyond Pluto happened to be looking past Jupiter during their observations and happened to discovery 12 new moons orbiting the giant planet. This is in contrast to other Jupiter moons such as Ganymede - the biggest in the solar system with a diameter of 5,268km. Sheppard's girlfriend came up with a name for it: Valetudo, the great-granddaughter of the Roman god Jupiter, and the goddess of health and hygiene. The stage is set, in other words, for possible moon-moon collisions.
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"It's allowed us to cover the whole area around Jupiter in a few shots, unlike before, and we're able to go fainter than people have been able to go before", says Sheppard. In fact, of Jupiter's 67 previously discovered moons, the 33 outermost moons all have retrograde orbits.
"This moon is going down the highway the wrong way", Sheppard said.
Depending on what survives from any such collision, Jupiter may then have even more moons. Sheppard's team speculates Valetudo could be a remnant of a collision between one or more moons. "Head-on collisions would quickly break apart and grind the objects down to dust". By this latest count, our solar system's largest planet now has 79 moons, more than any other. At the same time, they watched for Planet Nine or smaller, distant dwarf planets in the background.
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.
"Jupiter was well-placed in the sky to kill two birds with one stone", Sheppard said. Seven fall in a farther out "retrograde" cluster (red) rotating against the planet's spin, their opposing path kickstarted when ancient moons collided with comets, asteroids, or other moons.
Also, if the moons had formed earlier, there likely would have been more crashes, the team explained. Their existence shows that they were likely formed after this gas and dust dissipated.