The 19 - 43 metre wide asteroid 2015 KN57 will make a close pass (37.5 LD, 0.0965 AU) travelling at 9.15 km/second, to the Earth-Moon system on the 28th May 2015 @ 15:49 UT ±00:23.
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The Lunar Distance (LD), the distance between Earth and the Moon, equals 384,401 km, (or 0.00256 AU).