Asteroid 2013 SK20 passed the Earth at a distance of 872 000 km (roughly 2.3 times the distance between the Earth and the Moon) on Sunday 29 September 2013. The 15 m diameter object is thought to have an elliptical 493 day orbit which takes it outside that of Mars and in almost as far as the orbit of Venus. This means that it passes the Earth on a fairly regular basis, with the most recent close encounters having come in September 2009 and September 2005, and future close visits predicted in January 2022 and March 2026. It is not thought to present any serious threat to the Earth however, as an object this size would be predicted to burn up in the atmosphere at an altitude of about 26 km, with only fragmentary material reaching the ground.
The orbit of 2013 SK20. JPL Small Body Database Browser.
2013 SK20 was only discovered this month; the name 2013 SK20 means the 510th object discovered in the second half of September 2013 (period 2013 S). It has an average distance from the Sun (semi-major axis) greater than that of the Earth, but passes inside of the Earth's orbit, making it a member of the Apollo Group of asteroids.
See also The Eulalia and Polana asteroid families, Asteroid 2013 RZ53 passes between the Earth and the Moon, Asteroid 2013 RF74 passes the Earth, Asteroid 2013 RM73 passes the Earth and Asteroid 2013 RT73 flies past the Earth.
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