99942 Apophis
(99942) Apophis (symbol .svg){kind=small}
) is a near-Earth asteroid that worried people for a short time in December 2004. This was because observations seemed to show that it would hit the Earth in 2029. Other observations had more accurate, or better, ideas. During 2029, Apophis would go through a "gravitational keyhole", an area in space no more than about 400 meters across. This would make it hit the Earth on April 13, 2036. This danger made the asteroid Level 1 on the Torino impact hazard scale until August 2006.
More watching showed scientists that the "keyhole" would be missed. On August 5, 2006, Apophis was lowered to a Level 0 on the Torino Scale. As of October 19 2006 the probability that Apophis will hit the Earth on April 13, 2036 is something around 1 in 45,000. It may also hit in 2038, but however the probability for that encounter, or meeting, is 1 in 12.3 million.
More reading
Cooke, Bill. (2006) Fatal attraction. Astronomy, May 2006, pp. 46-51.
99942 Apophis Media
PIA23195-AsteroidApophis-ClosestApproachToEarth-20190429
Comparison between the best-fit convex and nonconvex shape models, and some of the available radar images of (99942) Apophis
Comparison of possible size of Apophis asteroid to Eiffel Tower and Empire State Building
Illustration of a common trend where progressively reduced uncertainty regions result in an asteroid impact probability increasing followed by a sharp decrease
Image sequence of asteroid (99942) Apophis, taken on 28 February 2021 with the 0.25-m Ritchey-Chretien telescope and QHY42 camera by G. Wells and D. Bamberger at Northolt Branch Observatories.
Hypothetical risk corridor for an impact on 13 April 2029, based on the 2020–21 planetary defense exercise
Asteroid 99942 Apophis – radar observations March 8–10, 2021 (March 26, 2021)
Other websites
Risk assessment
These sources are updated as new orbital data becomes available:
- http://neo.jpl.nasa.gov/risk/a99942.html Archived 2013-05-12 at the Wayback Machine (NASA JPL)
- 2004 MN4 page and 2004 MN4 impactor table from NEODyS.
NASA
- http://neo.jpl.nasa.gov/news/news146.html Archived 2007-08-18 at the Wayback Machine (JPL)
- http://neo.jpl.nasa.gov/news/news148.html Archived 2011-01-13 at the Wayback Machine (JPL)
- http://neo.jpl.nasa.gov/news/news149.html Archived 2007-06-21 at the Wayback Machine (JPL)
Other articles
- Closest Flyby of Large Asteroid to be Naked-Eye Visible (2029 approach)
- http://skyandtelescope.com/news/article_1458_1.asp Archived 2008-09-05 at the Wayback Machine (Sky and Telescope)
- An asteroid, headed our way (Christian Science Monitor, on efforts to deflect the asteroid if needed)