(450894) 2008 BT18

(450894) 2008 BT₁₈ is an eccentric, stony binary asteroid of the Apollo group, classified as near-Earth object and potentially hazardous asteroid, approximately 0.6 kilometers in diameter. It was discovered on 31 January 2008, by the U.S. LINEAR program at Lincoln Laboratory's Experimental Test Site, Socorro, New Mexico.

The S-type asteroid is also classified as a V-type by NASA's Infrared Telescope Facility, IRTF. It orbits the Sun at a distance of 0.9–3.5 AU once every 3 years and 4 months (1,210 days). Its orbit has an eccentricity of 0.59 and an inclination of 8° with respect to the ecliptic. The first precovery was taken at Palomar's Digital Sky Survey (DSS) in 1953, extending the asteroid's observation arc by 55 years prior to its discovery. The asteroid has a low Earth minimum orbit intersection distance of 0.0105 AU (1,570,000 km). On 14 July 2008, it transited Earth within 0.015 AU, or 5.9 lunar distances.

A rotational light-curve for this body was obtained from photometric observations made by astronomer Alberto Betzler at Salvador, Brazil, in July 2008. The fragmentary light-curve gave a rotation period of 7000272600000000000♠2.726±0.007 hours with a brightness variation of 0.04 in magnitude (U=1).

On 6 and 7 July 2008, research conducted using the Arecibo Observatory produced evidence that this is a binary system with an asteroid moon. The secondary component has a diameter of at least 200 meters, about 33% the size of and up to 1.5 kilometers apart from its primary. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 650 meters, based on an absolute magnitude of 18.3.