21088 Chelyabinsk (provisional designation 1992 BL2) is a stony asteroid and near-Earth object of the Amor group, approximately 4 kilometers in diameter.
It was discovered on 30 January 1992, by Belgian astronomer Eric Elst at ESO's La Silla Observatory in northern Chile.
A first precovery was taken during the Digitized Sky Survey at the Australia Siding Spring Observatory in January 1990, extending the asteroid's observation arc by 2 years prior to its official discovery at La Silla.
[5] Two rotational light-curves of Chelyabinsk were obtained by Czech astronomer Petr Pravec at Ondřejov Observatory in December 2002 and September 2004, respectively.
[4] The Collaborative Asteroid Lightcurve Link adopts Petr Pravec's revised WISE results, that is, a diameter of 4.23 kilometers and an albedo of 0.179 based on an absolute magnitude of 14.35.