Dig it: They’ve just discovered eight new moons orbiting Jupiter, bringing its total to 48. These days, they’ve started talking about Jupiter as its own little solar system. And even wackier — several of the moons circle the planet in the opposite direction to the others, which is freaking out many astronomists:

What is completely unknown about such irregular satellites is how they come to exist at all. When Jupiter was young, it is thought, many asteroids (or dynamical clusters) orbitted the Sun. As Jupiter condensed, its gravity began to bend the paths or even capture some of these stray asteroids. The best evidence for such a capture hypothesis is that many of these new satellites actually orbit in a direction opposite to the rotation of Jupiter, or otherwise follow what is known as retrograde orbits. Six of the new moons are retrograde.

But while the capture theory can explain the backwards orbits, that finding alone is only half the story of how actually to hold on to them once caught. The problem arises in slowing down the moon to a stable orbit. Following a large solar orbit requires lots of speed and energy, while going against the flow of Jupiter—if captured—is likely the only way to dissipate all that escape energy. At least for Jupiter in its present state, capture is almost impossible. As Jewitt noted: “The origin of the dissipation that lead to the capture of Jupiter’s irregular satellites is unknown. In fact, at the present time there is no plausible source of dissipation so that capturing satellites is presently almost impossible.”

I love outer space.

(Thanks to Slashdot for this one!)