One of a dozen new moons discovered around Jupiter is circling the planet on a suicide orbit that will inevitably lead to its violent destruction, astronomers say.
Researchers in the US stumbled upon the new moons while hunting for a mysterious ninth planet that is postulated to lurk far beyond the orbit of Neptune, the most distant planet in the solar system.
The team first glimpsed the moons in March last year from the Cerro Tololo Inter-American Observatory in Chile, but needed more than a year to confirm that the bodies were locked in orbit around the gas giant. “It was a long process,” said Scott Sheppard, who led the effort at the Carnegie Institution for Science in Washington DC.
Jupiter, the largest planet in the solar system, was hardly short of moons before the latest findings. The fresh haul of natural satellites brings the total number of Jovian moons to 79, more than are known to circle any other planet in our cosmic neighbourhood.
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. They are thought to be the remnants of larger parent bodies that were broken apart in collisions with asteroids, comets and other moons. Each takes about two years to circle the planet.
Two more of the moons are in a group that circle much closer to the planet in prograde orbits which travel in the same direction as Jupiter’s spin. Most likely to be pieces of a once larger moon that was broken up in orbit, they take nearly a year to complete a lap around Jupiter. Which direction the moons swing around the planet depends on how they were first captured by Jupiter’s gravitational field.
Astronomers describe the twelfth new Jovian moon as an “oddball”. Less than a kilometre wide, the tiny body circles Jupiter on a prograde orbit but at a distance that means it crosses the path of other moons hurtling towards it. Scientists have named the new moon Valetudo after the Roman god Jupiter’s great-granddaughter, the goddess of health and hygiene. But given the impending violence, it may be more than coincidence that Vale Tudo, which translates from Portuguese as “anything goes”, is an early form of full-contact mixed martial arts.
“Valetudo is like driving down the highway on the wrong side of the road,” said Sheppard. “It is moving prograde while all the other objects at a similar distance from Jupiter are moving retrograde. Thus head-on collisions are likely.”