On 15 February 2013 at about 9.20 am Yekaterinburg Time (about 3.20 am GMT), a large object entered the Earth's atmosphere over southern Russia at about 67 000 km per hour (almost 60 times the speed of sound) exploding over the province of Chelyabinsk at an altitude of about 23.3 km, generating a shock wave that shattered buildings in six cities, leading to about 1500 people being injured (this is the first ever recorded event in which people have been injured by a meteorite). It is estimated that the object was between 17 and 20 m in diameter and 12 000-13 000 kg in mass, though only about 650 kg of fragmentary material was recovered on the ground despite an extensive search, suggesting that less than 1000 kg reached the Earth's surface.
The trail of the Chelyabinsk Meteor, taken 2-3 minutes after it exploded. T.T. Uragan/Wikimedia Commons.
In a paper published on the online arXiv database at Cornell University Library on 10 August 2013, and submitted to the Monthly Notices of the Royal Astronomical Society, Carlos and Raúl de la Fuente Marcos of the Universidad Complutense de Madrid attempt to calculate the trajectory of the object prior to its encounter with the Earth, in order to determine its origins.
De la Fuente Marcos & de la Fuente Marcos calculate that the Chelyabinsk meteor shared a common origin with the Apollo Group Asteroid 2011 EO40, around 20-40 000 years ago. They also suggest that several other known asteroids, 2007 BD7, 2008 FH and 2010 DU1 as well as a number of smaller objects, may be part of the same family, which they describe as the Chelyabinsk Asteroid Family, although they not that these objects have perturbed orbits due to frequent encounters with Venus, the Earth-Moon System, Mars and Ceres.
The orbit of 2011 EO40. JPL Small Body Database Browser.
De la Fuente Marcos & de la Fuente Marcos suggest that to be considered a member of the Chelyabinsk Asteroid Family an asteroid should have a semi major access (average distance from the Sun) of 1.66 ± 0.08 au (i.e. 1.66 times the distance between the Earth and the Sun, give or take 0.08 times the distance between the Earth and the Sun), an eccentricity of 0.54 ± 0.02 (on a scale where 0 is a circular orbit and 1 a parabolic path that escapes from orbit) and an inclination of 3.7 ± 1.3° to the plane of the Solar System.
The orbit of 2007 BD7. JPL Small Body Database Browser.
See also The Eulalia and Polana asteroid families, The nature and history of 'Quasi-Hilda Object' 2000 YN30, The dust tail of 3200 Phaethon, Four more asteroids found to be co-orbitals of Neptune and 2012 LZ1; bigger than we thought.
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