Approaching asteroid has its own moon

New Scientist : Asteroid 1998 QE2âmdash;discovered in 1998, as its designation suggestsâmdash;is passing Earth today at a distance of 5.8 million km, or just over 5 times the distance between the Moon and Earth. It will be close enough to be observed by ground-based telescopes. On 29 May, the Deep Space Network antenna in Goldstone, California, took several pictures of the asteroid and discovered a second, smaller asteroid in orbit around the main body. The pictures suggest that the larger of the asteroids is 2.7 km across and the smaller is just 600 m. Although asteroid pairs and triplets aren’t unusual, they rarely pass near Earth. Astronomers can use the object orbiting the larger body to calculate the main asteroid’s density and determine whether the asteroid is a solid rock or a loose collection of pieces.