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99942 Apophis (provisional designation 2004 MN 4) is a near-Earth asteroid and a potentially hazardous object, 450 metres (1,480 ft) by 170 metres (560 ft) in size, [3] that caused a brief period of concern in December 2004 when initial observations indicated a probability of 2.7% that it would hit Earth on Friday, 13 April 2029.
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Radar Observations Refine the Future Motion of Asteroid 2004 MN4 (NASA News 149 : February 3, 2005) Transferred from en.wikipedia to Commons by Sreejithk2000 using CommonsHelper . ( Original text: Created by me manually to copy :Image:2004mn4d4_s.gif .
The only numbered objects with observation arcs of several years are (29075) 1950 DA and 101955 Bennu. [1] Notable asteroids removed from Sentry include (most recently removed listed first): 99942 Apophis, (410777) 2009 FD, 2006 QV 89, 2017 XO 2, 1994 WR 12, 2007 VK 184, 2013 BP 73, 2008 CK 70, 2013 TV 135, 2011 BT 15, 367943 Duende, and 2011 AG 5.
The radar images revealed that the asteroid has a bilobate shape. [11] February 2021 observations of 2001 FO 32 by the La Silla Observatory show that it displays a light curve amplitude of 0.9 magnitudes. [12] The preliminary photometry indicates that the body is tumbling with a long main rotation period of 39.89 ± 0.05 hours. [4]
One example of such a follow-up observation was for 3671 Dionysus by UKIRT, the world's largest infrared telescope at the time (1997). [64] A second example was the 2013 ESA Herschel Space Observatory follow-up observations of 99942 Apophis, which showed it was 20% larger and 75% more massive than previously estimated. [65]
It gained some public interest when it became clear, in January 2005, that the asteroid 99942 Apophis would miss the Earth in 2029 but may go through one or another keyhole leading to impacts in 2036 or 2037. Further research has since been done, however, which revealed the probability of Apophis passing through the keyhole was extremely low. [1]
99942 Apophis – a near-Earth asteroid that will pass within geosynchronous orbit in 2029. Radar astrometry from observations by Ostro's group have been essential to predicting Apophis' trajectory. To explore the dynamical implications of these observations in detail, Ostro collaborated with Steven Chesley, Jon D. Giorgini, Scott Hudson , Jean ...