(523972) 1999 CW₈, provisional designation 1999 CW₈, is a bright carbonaceous asteroid and sub-kilometer near-Earth object of the Apollo group, first observed on 12 February 1999, by astronomers of the Lincoln Near Earth Asteroid Research program at Lincoln Laboratory ETS in New Mexico, United States.^[1]

This minor planet was numbered by the Minor Planet Center on 18 May 2019 (M.P.C. 114615). As of 2019, it has not been named.^[4]

1999 CW₈ is an Apollo asteroid that crosses Earth's orbit. It orbits the Sun at a distance of 0.9–3.6 AU once every 3 years and 4 months (1,221 days; semi-major axis of 2.24 AU). Its orbit has an eccentricity of 0.60 and an inclination of 34° with respect to the ecliptic.^[2] The asteroid never approaches Earth closer than 0.2 AU in the foreseeable future, but occasionally makes close approaches to Mars of 0.07 AU. It makes one such approach in 2073, at 0.067 AU, and another one in 2103, at 0.094 AU. Due to 1999 CW₈'s relatively high inclination, although it passes closer to the Sun than the Earth (0.9 AU), it never comes closer than 0.2 AU.

It is a carbonaceous B-type asteroid, relatively rare in the asteroid belt but common in the inner Solar System.^[2] Based on an absolute magnitude of 18.6,^[1][2] and an assumed albedo of 0.159 (derived from the B-type asteroid 2 Pallas), the asteroid can be estimated to have a mean-diameter of approximately 640 meters.^[3] If it impacted the Earth would cause significant damage, but not as much as the Cretaceous–Paleogene extinction event progenitor, which brought about a mass extinction, as it is only 1/20 to 1/10 the size. However, it is unlikely to come close enough to Earth to impact it, or even become a risk of impact.

• Mars-crossing asteroid