A pair of asteroids are set to make close passes by the Earth this week, and both are unusually large for visitors to the neighborhoods they’ll be cruising through. One may even be visible with little more than binoculars.
A close encounter with an asteroid of this size is only expected to happen about once a decade, so many astronomers and amateurs are planning to observe the fly-by. Thenotes another interesting characteristic of 2011 UL21 is its “11:34 resonance” with Earth, which means it orbits the sun 11 times in just about the same amount of time it takes our planet to go around the star 34 times. This makes for some cool visualizations of both objects.