The 37 - 82 metre wide asteroid 2007 WZ4 will make a close pass (54.9 LD, 0.1411 AU) travelling at 8.91 km/second, to the Earth-Moon system on the 21st August 2015 @ 11:08 UT ±2 days 00:18.
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The Lunar Distance (LD), the distance between Earth and the Moon, equals 384,401 km, (or 0.00256 AU).