* Astronomy

The 54 - 120 metre wide asteroid 2013 RL43 will make a close pass (13.0 lunar distances, 0.0333 AU), travelling at 25.92 km/second, to the Earth-Moon system on the 21st September, 2013 @ 21:57 UT ±00:01. 

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The Lunar Distance (LD), the distance between Earth and the Moon, equals 384,401 km, (or 0.00256 AU).