Galileo's Pendulum

Today, a relatively large asteroid known as 1998 QE2 will pass Earth, beyond the orbit of the Moon. Yes, it’s named for the cruise ship, but it’s much bigger — 2.7 kilometers along its greatest axis — and correspondingly much more massive. (As I said, the asteroid won’t come even as close as the Moon, so even though 1998 QE2 would be pretty devastating if it hit us, we’re in absolutely no danger.) If you have a telescope and you want more information on how to see the asteroid for yourself, check out David Dickinson’s guide at Universe Today.

The exciting thing for me is the discovery of a small moon orbiting the asteroid. Radar data showed a small body moving around the larger asteroid, which in the video below and image shows up as a bright spot. (Based on the fact that 1998 QE2 is named for a ship named for Queen Elizabeth, I’m tempted to make a Prince Charles/dinghy joke, but I’ll spare you.) This isn’t the first asteroid moon ever seen, but it’s still very cool — not least since it will eventually let astronomers estimate the mass of 1998 QE2. That mass will in turn give some information about the density and composition of the asteroid. The higher-resolution radar maps to come should also reveal more about the moon itself. Stay tuned!