# 2009 FD

Discovery[1] VLT image of the very faint near-Earth asteroid 2009 FD Observatorio Astronómico de La Sagra (J75) 16 March 2009 2009 FD Apollo NEO[2] Epoch 2013-Nov-04 (Uncertainty=0)[2] 1.7361 AU (Q) 0.58960 AU (q) 1.1628 AU (a) 0.49296 1.25 yr 196.02° (M) 3.1361° 9.4968° 281.30° ~472 meters (1,549 ft)[3][2][4] 8.3×1010 kg (assumed)[4] 5.87 h[2] 0.01 (dark)[2] 22.1[2]

2009 FD is an Apollo asteroid[2] (a class of near-Earth asteroid) with an orbit that places it at risk of a possible future collision with Earth. It has the highest impact threat on the Palermo Technical Impact Hazard Scale now that it is estimated to be 470 meters in diameter.[5] The asteroid was discovered on 16 March 2009.[1] 2009 FD made a close pass to Earth on 27 March 2009 at a distance of 0.004172 AU (624,100 km; 387,800 mi)[6][7] and another on 24 October 2010 at 0.0702 AU.[6] 2009 FD was recovered at apparent magnitude 23[note 1] on 30 November 2013 by Cerro Paranal Observatory,[8] several months before the close approach of April 2014 when it passed 0.1 AU from Earth.[6] It brightened to roughly apparent magnitude 19.3 around mid-March 2014.[9] One radar Doppler observation of 2009 FD was made in 2014.[2] The October–November 2015 Earth approach will be studied by the Goldstone Deep Space Network.[10]

NASA's Near Earth Program originally estimated its size to be 130 metres in diameter based on an assumed albedo of 0.15.[4] This gave it an estimated mass of around 2,800,000 tonnes.[11] But work by Amy Mainzer using NEOWISE data shows that it could be as large as 472 metres with an albedo as low as 0.01.[3][2] Because 2009 FD (K09F00D) was only detected in two (W1+W2) of the four wavelengths the suspected NEOWISE diameter is more of an upper limit.[3]

The JPL Small-Body Database shows that 2009 FD will make two very close approaches in the late 22nd century, with the approach of 29 March 2185 currently having a 1 in 385 chance of impacting Earth.[4] The nominal 2185 Earth approach distance is 0.009 AU (1,300,000 km; 840,000 mi).[6] Orbit determination for 2190 is complicated by the 2185 close approach.[6] The precise distance that it will pass from Earth and the Moon on 29 March 2185 will determine the 30 March 2190 distance. 2009 FD should pass closer to the Moon than Earth on 29 March 2185.[6] An impact by 2009 FD would cause severe devastation to a large region or tsunamis of significant size.[12] Due to 2009 FD's size, and its interactions with Mars and Venus, which increase its orbital uncertainty over time, it is rated −0.40 on the Palermo Scale, placing it high on the Sentry Risk Table.[5]

## Past Earth-impact estimates

In January 2011, near-Earth asteroid 2009 FD (with observations through 7 December 2010) was listed on the JPL Sentry Risk Table with a 1 in 435 chance of impacting Earth on 29 March 2185.[11] In 2014 (with observations through 5 February 2014 creating an observation arc of 1807 days) the potential 2185 impact was ruled out.[13] Using the 2014 observations, the Yarkovsky effect has become more significant than the position uncertainties.[14][15] The Yarkovsky effect has resulted in the 2185 virtual impactor returning.

## Notes

1. ^ At an apparent magnitude of 23, 2009 FD was roughly 4 million times fainter than can be seen with the naked eye.
Math: $(\sqrt[5]{100})^{23-6.5}\approx 3981071$

## References

1. ^ a b "MPEC 2009-F09 : 2009 FD". IAU Minor Planet Center. 2009-03-17. Retrieved 2013-01-09. (K09F00D)
2. "JPL Small-Body Database Browser: (2009 FD)". Jet Propulsion Laboratory. 2014-03-11 last obs (arc=5.04 yr). Retrieved 2014-02-10.
3. ^ a b c Mainzer, Amy; Bauer, J.; Grav, T.; Masiero, J. (2014). "The Population of Tiny Near-Earth Objects Observed by NEOWISE". The Astrophysical Journal 784 (2). arXiv:1310.2980. Bibcode:2014ApJ...784..110M. doi:10.1088/0004-637X/784/2/110. (listed as K09F00D)
4. ^ a b c d "Earth Impact Risk Summary: 2009 FD". NASA/JPL Near-Earth Object Program Office. Retrieved 2014-05-01.
5. ^ a b Sentry Risk Table
6. "JPL Close-Approach Data: (2009 FD)". 2014-04-07 last obs (arc=5.11 years). Retrieved 2014-05-01.
7. ^ Near Earth Asteroid 2009 FD - whilst you were sleeping! (ice in space)
8. ^ "2009 FD Orbit". IAU Minor Planet Center. Retrieved 2013-12-17.
9. ^ "2009 FD Ephemerides for 1 April 2014". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 2013-12-17.
10. ^ Dr. Lance A. M. Benner (2014-03-17). "Goldstone Asteroid Schedule". NASA/JPL Asteroid Radar Research. Retrieved 2014-03-21.
11. ^ a b "Earth Impact Risk Summary: 2009 FD (arc=650 days)". Wayback Machine: JPL. 2011-01-11 (computed on Dec 14, 2010). Retrieved 2014-02-14. (2.3e-03 = 1 in 435 chance)
12. ^ How a Near-Earth Object Impact Might Affect Society, 9 January 2003, Clark R. Chapman, SwRI, Boulder CO USA
13. ^ "Earth Impact Risk Summary: 2009 FD (arc=1807 days)". Wayback Machine: JPL. 2014-02-10 (computed on Feb 07, 2014). Retrieved 2014-05-01.
14. ^ "Sentry Notes". NASA/JPL Near-Earth Object Program Office. Retrieved 2014-05-01.
15. ^ "2009FD Impactor Table". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 2014-05-01. (2.64e-3 = 1 in 379 chance)