Apophis
Apophis belongs to a group called the "Aten asteroids", asteroids with an orbital semi-major axis less than one astronomical unit. This particular one has an orbital period about the Sun of 323 days, and its path brings it across Earth's orbit twice on each passage around the Sun.
Based upon the observed brightness, Apophis's length was estimated at 415 m (1350 ft); a more refined estimate based on spectroscopic observations at NASA's Infrared Telescope Facility in Hawaii by Binzel, Rivkin, Bus, and Tokunaga (2005) is 350 m (1150 ft). Its mass is estimated to be 4.6×1010 kg.
Apophis was discovered on June 19, 2004, by Roy A. Tucker, David J. Tholen, and Fabrizio Bernardi of the NASA-funded University of Hawaii Asteroid Survey from Kitt Peak National Observatory in Arizona. This group observed for two nights. The new object received the provisional designation 2004 MN4.
On December 18, the object was rediscovered from Australia by Gordon Garradd of the Siding Spring Survey, another NASA-funded NEA survey. Further observations from around the globe over the next several days allowed the Minor Planet Center to confirm the connection to the June discovery.
Based upon the observed brightness, Apophis's length was estimated at 415 m (1350 ft); a more refined estimate based on spectroscopic observations at NASA's Infrared Telescope Facility in Hawaii by Binzel, Rivkin, Bus, and Tokunaga (2005) is 350 m (1150 ft). Its mass is estimated to be 4.6×1010 kg.
Apophis was discovered on June 19, 2004, by Roy A. Tucker, David J. Tholen, and Fabrizio Bernardi of the NASA-funded University of Hawaii Asteroid Survey from Kitt Peak National Observatory in Arizona. This group observed for two nights. The new object received the provisional designation 2004 MN4.
On December 18, the object was rediscovered from Australia by Gordon Garradd of the Siding Spring Survey, another NASA-funded NEA survey. Further observations from around the globe over the next several days allowed the Minor Planet Center to confirm the connection to the June discovery.
Naming
When first discovered, the object received the provisional designation 2004 MN4 (sometimes written 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), the first numbered asteroid with Earth-impact solutions (to its orbit determination from observations).
Receiving a permanent number made it eligible for naming, and it promptly received the name "Apophis" as of July 19, 2005. Apophis is the Greek name of the Ancient Egyptian god Apep, "the Destroyer", who dwells in the eternal darkness of the Duat (underworld) and tries to destroy the Sun during its nightly passage.
When first discovered, the object received the provisional designation 2004 MN4 (sometimes written 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), the first numbered asteroid with Earth-impact solutions (to its orbit determination from observations).
Receiving a permanent number made it eligible for naming, and it promptly received the name "Apophis" as of July 19, 2005. Apophis is the Greek name of the Ancient Egyptian god Apep, "the Destroyer", who dwells in the eternal darkness of the Duat (underworld) and tries to destroy the Sun during its nightly passage.
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