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(410777) 2009 FD (also written as 2009 FD) is a binary〔〔http://www.naic.edu/~pradar/〕 Apollo asteroid〔 (a class of near-Earth asteroid) with an orbit that places it at risk of a possible future collision with Earth in 2185. It has the highest impact threat of all known asteroids on the Palermo Technical Impact Hazard Scale based on its estimated diameter of 470 meters, kinetic yield, impact probability, and time interval.〔 (410777) 2009 FD was initially announced as discovered on 16 March 2009 by La Sagra Sky Survey.〔 Because there were previous observations found in images taken by the Spacewatch survey some 3 weeks prior, on 24 February 2009, the Minor Planet Center assigned the discovery credit to Spacewatch under the discovery assignment rules.〔〔 (410777) 2009 FD made a close pass to Earth on 27 March 2009 at a distance of 〔〔(Near Earth Asteroid 2009 FD - whilst you were sleeping! (ice in space) )〕 and another on 24 October 2010 at 0.0702 AU.〔 (410777) 2009 FD was recovered at apparent magnitude 23〔At an apparent magnitude of 23, (410777) 2009 FD was roughly 4 million times fainter than can be seen with the naked eye. Math: 〕 on 30 November 2013 by Cerro Paranal Observatory,〔 several months before the close approach of April 2014 when it passed 0.1 AU from Earth.〔 It brightened to roughly apparent magnitude 19.3 around mid-March 2014.〔 One radar Doppler observation of (410777) 2009 FD was made in 2014.〔 The October–November 2015 Earth approach will be studied by the Goldstone Deep Space Network.〔 NASA's Near Earth Program originally estimated its size to be 130 metres in diameter based on an assumed albedo of 0.15.〔 This gave it an estimated mass of around 2,800,000 tonnes.〔 But work by Amy Mainzer using NEOWISE data in 2014 showed that it could be as large as 472 metres with an albedo as low as 0.01.〔〔 Because (410777) 2009 FD (K09F00D) was only detected in two (W1+W2) of the four wavelengths the suspected NEOWISE diameter is more of an upper limit.〔 Radar observations in 2015 showed it to be a binary asteroid.〔 The primary is 120–180 meters in diameter and the secondary is 60–120 meters in diameter.〔 The JPL Small-Body Database shows that (410777) 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.〔 The nominal 2185 Earth approach distance is .〔 Orbit determination for 2190 is complicated by the 2185 close approach.〔 The precise distance that it will pass from Earth and the Moon on 29 March 2185 will determine the 30 March 2190 distance. (410777) 2009 FD should pass closer to the Moon than Earth on 29 March 2185.〔 An impact by (410777) 2009 FD would cause severe devastation to a large region or tsunamis of significant size.〔(How a Near-Earth Object Impact Might Affect Society, 9 January 2003, Clark R. Chapman, SwRI, Boulder CO USA )〕 Due to (410777) 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 higher on the Sentry Risk Table than any other known object.〔(Sentry Risk Table )〕 == Past Earth-impact estimates == In January 2011, near-Earth asteroid (410777) 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.〔 In 2014 (with observations through 5 February 2014 creating an observation arc of 1807 days) the potential 2185 impact was ruled out.〔 Using the 2014 observations, the Yarkovsky effect has become more significant than the position uncertainties.〔〔〔 The Yarkovsky effect has resulted in the 2185 virtual impactor returning. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「(410777) 2009 FD」の詳細全文を読む スポンサード リンク
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