On April 13, 2029, Apophis will pass about 32,250 km from Earth's surface. Apophis was discovered on June 19, 2004 by Roy Tucker, David Tholen and Fabrizio Bernardi of the University of Hawaii Asteroid Survey. The object was re-discovered on December 18, 2004 by Gordon Garradd of the Siding Spring Survey. It was quickly determined that Apophis had a very real chance of hitting the Earth on April 13, 2029.

When the media broke with the story, the odds were set at about 1 in 300 that the asteroid would strike the Earth on that date. Later that same day, further observations caused the probability to rise to 1 in 62 that a collision would take place. Then, on December 27th, as the world witnessed the devistation of the Indian Ocean tsunami, the odds of this asteroid slamming into Earth were raised again to 1 in 37. This asteroid was believed to have a 2.7 percent chance of striking Earth, perhaps creating tsunamis that dwarfed anything the Earth has ever experienced in recorded history. But later that day, a pre-discovery picture of Apophis allowed astronomers to downgrade the threat of an impact to only 0.004 percent, a near-certain miss.

On April 13, 2029, the world should witness a rare event. Apophis will become a naked-eye object for observers in Europe and parts of Africa and Brazil. It will appear like a slow-moving satellite in the night sky.

The simulation A2004MN4.gsim shows Apophis as it visits the Earth / Moon system. Watch as it approaches the Earth / Moon system from the right of the screen. It makes its closest pass to Earth on April 13th at 21:45 GMT, when it passes 32,250 kilometers from Earth's surface. Earth's gravity noticably bends Apophis' trajectory. Eighteen hours later, Apophis will pass 79,319 kilometers above the Moon's south pole.

Starting conditions for this simulation were generated by JPL Horizons Ephemeris Computation Service.

Download A2004MN4.gsim

(You need to have the program Gravity Simulator installed on your computer first. Click Here to download Gravity Simulator.)