Scientists working with NASA's 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, California, say that the large asteroid that just past by Earth actually has a moon. The 1100 foot asteroid came within 745,000 miles of Earth, roughly 3 times the distance from the Earth to the moon, at 10:19 a.m. CST on January 26.
But what may shock you is that large asteroids having a circulating moon, or even two, aren't all that uncommon. Scientists have discovered that roughly 16 percent of asteroids that are about 650 feet or larger are binary, which means there is a smaller asteroid moon orbiting the larger one. In some cases 2 or even 3 moons have been seen.
The trajectory of this asteroid, called 2004 BL86, is well understood. Monday's flyby was the closest approach the asteroid will make to Earth for at least the next two centuries. It is also the closest a known asteroid this size will come to Earth until asteroid 1999 AN10 flies past our planet in 2027. The problem with that statement is that scientists have only discovered about a thousand near earth orbiting asteroids, with dozens more spotted month after month. While that may sound like a lot, in reality the actual number of near Earth orbiting asteroids is likely much higher. Some in the science community believe there could be hundreds of thousands. Many of these unknown orbiters likely haven't flown past Earth yet as they have a MUCH larger orbit than others.