On May 31, 2013 at 20:59 UTC, the 2.7 km wide Asteroid 1998 QE2 will make its closest approach to Earth at 5.8 million kilometers (3.6 million miles). This will be the closest it gets to Earth for at least the next two centuries.
Latest NASA's radar observations just discovered that 1998 QE2 is actually a binary system asteroid. A series of radar images from 70 meter-wide (230-foot) Deep Space Network antenna at Goldstone revealed on May 29/30, 2013 that approaching asteroid has its own moon. According to NASA, orbiting satellite is estimated to be 600 meters (2,000 feet) wide. Scientists were surprized by discovery, however, asteroid binary systems is not uncommon. About 16% of near-Earth asteroids are binary or even triple systems.
Asteroid's satellites helps scientist to get an even more precise mass estimate of the asteroid. Obtained radar images also revealed dark features on the surface of Asteroid 1998 QE2, which suggest it has several large concavities, probably impact craters. Another discovery was that its rotation speed is more slowly than originally thought.
First radar images of asteroid 1998 QE2 obtained on May 30, 2013 by Goldstone's Deep Space Antenna Network telescope (Credit: NASA/JPL-Caltech/GSSR)
Huge asteroid will only get to a brightness of about magnitude 10, making it unvisible to the unaided eye. 1998 QE2 will be a prime target for radar observations. Deep Space Network antenna in Goldstone, US and Arecibo Observatory in Puerto Rico will observe 1998 QE2 until June 9, 2013, when the asteroid enters northern skies.
Asteroid 1998 QE2 orbit diagram showing its closest approach to our planet on May 31, 2013. (Credit: NASA/JPL Small-Body Database Browser)