Apophis was discovered on June 19, 2004, by Roy A. Tucker, David J. Tholen and Fabrizio Bernardi at the Kitt Peak National Observatory. On D...
Apophis was discovered on June 19, 2004, by Roy A. Tucker, David J. Tholen and Fabrizio Bernardi at the Kitt Peak National Observatory. On December 21, 2004, Apophis passed 0.0963 AU (14,410,000 km; 8,950,000 mi) from Earth. Precovery observations from March 15, 2004, were identified on December 27, and an improved orbit was computed. Radar astrometry in January 2005 further refined the orbit.nWhen first discovered, the object received the provisional designation 2004 MN4, and news and scientific articles about it referred to it by that name. When its orbit was sufficiently well calculated, it received the permanent number 99942 (on June 24, 2005). Receiving a permanent number made it eligible for naming, and it received the name "Apophis" on July 19, 2005. Apophis is the Greek name of an enemy of the Ancient Egyptian sun-god Ra: Apep, the Uncreator, an evil serpent that dwells in the eternal darkness of the Duat and tries to swallow Ra during his nightly passage. Apep is held at bay by Set, the Ancient Egyptian god of storms and the desert. David J. Tholen and Tucker—two of the co-discoverers of the asteroid—are reportedly fans of the TV series Stargate SG-1. One of the show's persistent villains is an alien named Apophis. In the fictional world of the show, the alien's backstory was that he had lived on Earth during ancient times and had posed as a god, thereby giving rise to the myth of the Egyptian god of the same name.nClose approachesnnClose approach of Apophis on April 13, 2029 (as known in February 2005)nnAfter the Minor Planet Center confirmed the June discovery of Apophis, an April 13, 2029 close approach was flagged by NASA's automatic Sentry system and NEODyS, a similar automatic program run by the University of Pisa and the University of Valladolid. On that date, it will become as bright as magnitude 3.4 (visible to the naked eye from rural as well as darker suburban areas, visible with binoculars from most locations). The close approach will be visible from Europe, Africa, and western Asia. During the close approach in 2029 Earth will perturb Apophis from an Aten class orbit with a semi-major axis of 0.92 AU to an Apollo class orbit with a semi-major axis of 1.1 AU.nAfter Sentry and NEODyS announced the possible impact, additional observations decreased the uncertainty in Apophis's trajectory. As they did, the probability of an impact event temporarily climbed, peaking at 2.7% (1 in 37).This probability, combined with its size, caused Apophis to be assessed at level 4 on the Torino Scale, and 1.10 on the Palermo Technical Impact Hazard Scale, scales scientists use to represent how dangerous a given asteroid is to Earth. These are the highest values for which any object has been rated on either scale. The chance that there would be an impact in 2029 was eliminated by December 27, 2004. The danger of a 2036 passage was lowered to level 0 on the Torino Scale in August 2006. With a cumulative Palermo Scale rating of −3.2,[3] the risk of impact from Apophis is less than one thousandth the background hazard level.nOn April 13, 2029, Apophis will pass Earth within the orbits of geosynchronous communication satellites, but will come no closer than 19,400 miles (31,300 kilometers) above Earth's surface. The 2029 pass will be much closer than had first been predicted. The pass in late March 2036 will be no closer than about 23 million kilometres (14×106 mi) — and will probably miss us by something closer to 56 million kilometres (35×106 mi).n2005 and 2011 observationsnIn July 2005, former Apollo astronaut Rusty Schweickart, as chairman of the B612 Foundation, formally asked NASA to investigate the possibility that the asteroid's post-2029 orbit could be in orbital resonance with Earth, which would increase the probability of future impacts. Schweickart also asked NASA to investigate whether a transponder should be placed on the asteroid to enable more accurate tracking of how its orbit is affected by the Yarkovsky effect. On January 31, 2011, astronomers took the first new images of Apophis in more than 3 years Less
