The 23 - 52 metre wide asteroid 2007 PS25 will make a close pass (19.3 lunar distances, 0.0497 AU), travelling at 8.50 km/second, to the Earth-Moon system on the 6th September, 2012 @ 12:15 UT ±23:54.
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The Lunar Distance (LD), the distance between Earth and the Moon, equals 384,401 km, (or 0.00256 AU).