The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo , discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Earth (a > 1 AU ) but perihelion distances less than the Earth's aphelion distance (q < 1.017 AU).
5-616: 2007 TU 24 is an Apollo near-Earth asteroid that was discovered by the Catalina Sky Survey in Arizona on 11 October 2007. Imaging radar has estimated that it is 250 meters (820 ft) in diameter. The asteroid passed 554,209 kilometer (344,370 mile or 1.4- lunar distance ) from Earth on 29 January 2008 at 08:33 UTC . (At the time of the passage it was believed the closest for any known potentially hazardous asteroid (PHA) of this size before 2027, but in 2010 2005 YU 55
10-472: The Aten , Amor and Atira asteroids), of which 1,628 are numbered (asteroids are not numbered until they have been observed at two or more oppositions ), 79 are named, and 2,104 are identified as potentially hazardous asteroids . The closer their semi-major axis is to Earth's, the less eccentricity is needed for the orbits to cross. The Chelyabinsk meteor , that exploded over the city of Chelyabinsk in
15-546: The asteroid has an observation arc of about 3 years and the trajectory is well defined. It was removed from the Sentry Risk Table on 4 December 2007 at 14:05 UTC . Goldstone Observatory carried out radar observations on January 23 and 24 January 2008. As of then, the orbit of the asteroid was known with such a high precision that scientists were able to calculate close approaches from the year 67 AD to 2141 AD. On 29 January 2008 at 08:33 UTC , 2007 TU 24 passed by
20-406: The earth at a nominal distance of 0.0037043 AU (554,160 km ; 344,340 mi ) with a relative speed of 9.248 km/s . Observations from Arecibo Observatory were taken on 1–4 February. It is a contact binary asteroid . Apollo asteroid As of October 2024 , the number of known Apollo asteroids is 20,412, making the class the largest group of near-Earth objects ( cf .
25-402: Was measured to be 400 meters in diameter.) At closest approach 2007 TU24 had an apparent magnitude of 10.3 and was about 50 times fainter than the naked eye can see. It required about a 3-inch (76 mm) telescope to be seen. From the date of discovery of asteroid 2007 TU 24 on 11 October 2007, a total of 316 observations of it had been made by 31 January 2008, spanning 112 days. Now
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