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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.
Apophis hitting Earth is possible, study finds, but very unlikely Astronomers have long had their eye on the notorious Apophis, which was initially believed to pose a serious threat to Earth upon ...
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]
For example, it was estimated there was a high chance of 99942 Apophis swinging by Earth in 2029 with a 10 −4 probability of returning on an impact trajectory in 2035 or 2036. It was then determined that a deflection from this potential return trajectory, several years before the swing-by, could be achieved with a velocity change on the order ...
During the first decade of the 2000s, there were serious concerns the 325 metres (1,066 ft) wide asteroid 99942 Apophis posed a risk of impacting Earth in 2036. Preliminary, incomplete data by astronomers using ground-based sky surveys resulted in the calculation of a Level 4 risk on the Torino Scale impact hazard chart .
BTW, the "keyhole" threat of Apophis has been rebuked 5 years ago, according to its WP article: "However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole, a precise region in space no more than about a half-mile wide,[6] that would set up a future impact on April 13, 2036.
The Torino scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets.It is intended as a communication tool for astronomers and the public to assess the seriousness of collision predictions, by combining probability statistics and known kinetic damage potentials into a single threat value.
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] However such follow-ups are rare. The size estimates of most near-Earth asteroids are based on visible light only. [66]