* Astronomy

Orbital elements:
2009 ST171                                               Earth MOID = 0.0274 AU
Epoch 2009 June 18.0 TT = JDT 2455000.5                 MPC
M 330.28088              (2000.0)            P               Q
n   0.23723185     Peri.  205.88087     +0.84355286     -0.53699358
a   2.5843662      Node   186.61334     +0.50336555     +0.79544948
e   0.6081273      Incl.    3.74097     +0.18719426     +0.28088792
P   4.15           H   26.8           G   0.15           U   7

MPEC 2009 - S133

2009 ST171 Earth Impact Risk Summary
Torino Scale (maximum) 0 Palermo Scale (maximum) -6.62 Palermo Scale (cumulative) -6.62 Impact Probability (cumulative) 2.3e-06 Number of Potential Impacts 1	Vimpact 14.86 km/s Vinfinity 9.83 km/s H 26.8 Diameter 0.015 km Mass 4.3e+06 kg Energy 1.1e-01 MT all above are mean values weighted by impact probability
Analysis based on 19 observations spanning 1.1579 days (2009-Sep-28.23931 to 2009-Sep-29.39719)

The 12 - 26 metre wide asteroid 2009 ST171 will make a close pass (15.8 Lunar Distances, 0.0407 AU), travelling at 8.71 km/s, to the Earth-Moon system on the 5th October, 2009.

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