(99942) Apophis 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.
Further reading [change]
Cooke, Bill. (2006) Fatal attraction. Astronomy, May 2006, 46-51.
Other websites [change]
Risk assessment [change]
These sources are updated as new orbital data becomes available:
- May we deflect asteroids? (Advanced Concepts Team)
- Near-Earth Asteroid 2004 MN4 Reaches Highest Score To Date On Hazard Scale (JPL)
- Possibility of an Earth Impact in 2029 Ruled Out for Asteroid 2004 MN4 (JPL)
- Radar Observations Refine the Future Motion of Asteroid 2004 MN4 (JPL)
- Animation explaining how impact risk is determined from 
Older articles [change]
- Whew! Asteroid Won't Hit Earth in 2029, Scientists Now Say (SPACE.com)
- Asteroid Watch: Odds of 2029 Collision Stuck at 1-in-40 (SPACE.com)
- Worrisome Asteroid Underscores Planetary Defense Mission (SPACE.com)
More recent articles [change]
- Astronauts propose 'tractor-pull' of asteroid
- Closest Flyby of Large Asteroid to be Naked-Eye Visible (2029 approach)
- Asteroid 2004 MN4: A Really Near Miss! (Sky and Telescope)
- An asteroid, headed our way (Christian Science Monitor, on efforts to deflect the asteroid if needed)
- Astronauts want plan to prevent cosmic collision
- U.N. urged to take action on asteroid threat