(458732) 2011 MD5 is an Apollo near-Earth asteroid around 1.2 kilometers (0.75 miles) in diameter. It is the largest asteroid known to have passed closer than the Moon. On 17 September 1918 the asteroid passed 0.00234 AU (350 thousand km; 0.91 LD) from Earth with a peak apparent magnitude of around 8.4. The 1918 close approach distance is known with an accuracy of roughly ±200 km. The asteroid had come to opposition (opposite the Sun in the sky) on 9 August 1918 at magnitude 16.