Throwback Thursday: Earth’s second moon? (Synopsis)

“The moon was like this awesome, romantic, mysterious thing, hanging up there in the sky where you could never reach it, no matter how much you wanted to. But you’re right. Once you’re actually here, it’s just a big, dull rock.” -Futurama

Oh, but the big dull rocks are fascinating in their own right. Especially, mind you, when there are more of them than we ever expected. Jupiter, for example, has not only all the moons that orbit around it, but a whole slew of gravitationally captured objects -- the Trojans (and Greeks) -- that orbit in front and behind it.

Image credit: Petr Scheirich, 2005, with Trojans (and Greeks) shown in Green.

While Earth may have only one true moon orbiting our world, what of these Trojans? Do we have any captured asteroids or comets hanging out around one of our Lagrange points?

Image credit: Neil J. Cornish / NASA / WMAP science team, via http://map.gsfc.nasa.gov/mission/observatory_l2.html.

We absolutely do, but only one of them is here to stay, and it very likely isn't the one -- 3753 Cruithne -- you heard of. Check it out!