Astronomers Find a Staggering 12 New Moons Orbiting Jupiter
Jul 19 2018
Jupiter's largest moon, Ganymede, is the ninth-largest object in the solar system, bigger than the planet Mercury and dwarf planets like Pluto.
The discovery brings Jupiter's total number of known moons to a whopping 79 - the most of any planet in our Solar System.
Sheppard said these moons were probably objects that formed near Jupiter during the early days of the solar system and were "captured" by the planet's strong gravitational pull.
As a result, head on collisions are much more likely to occur between this "oddball" prograde moon and its retrograde cousins moving in opposite directions. "It's also likely Jupiter's smallest known moon, being less than one kilometre in diameter". But the moon Sheppard and his colleagues call "oddball" is different - instead of orbiting with the other prograde moons, its orbit takes it out as far as the retrograde moons.
Because Valetudo's orbit crosses the orbits of some of the outer retrograde moons, it's possible that it suffered a head-on collision in the past.
A head-on collision between two moons would "grind the objects down to dust", he added.
All the moons may be fragments that broke apart when their larger, parent cosmic bodies collided. As they reported Tuesday in an online notice from International Astronomical Union, all 12 have now been confirmed by other telescopes.
Depending on what survives from any such collision, Jupiter may then have even more moons.
Several other telescopes were used to confirm the finds, including the 6.5-meter Magellan telescope at Carnegie's Las Campanas Observatory, also in Chile. Jupiter happened to be in the same field of view, so they also looked for any as yet unknown moons. The smallest moon is just over a half-mile across, while the largest is about three miles in diameter. The researchers proposed naming the unique find Valetudo after the Roman god Jupiter's great-grandaughter.
The discovery of this collection of moons was actually made by accident as the team had been observing further into space in the hope of finding 'Planet Nine', the so-far theoretical planet that could exist at the farthest-flung part of our solar system. "By looking at these outer moons", he said, "we can get an insight into what the objects were like that ended up forming the planets we see today".
Before Sheppard's team conducted their survey, there were 69 known Jovian moons, but there's always been reason to believe there are quite a few more.
Valetudo is more distant and more inclined than the prograde group of moons and takes about 1.5 years to orbit Jupiter.
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.
"If we do find this planet in the next few years, it would be a pretty awesome discovery for astronomy". "Maybe there will have to be a new definition for the smaller moons". The outer moons move in the opposite direction - a retrograde orbit.
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.