(458732) 2011 MD5 is an Apollonear-Earth asteroid around 1.2 kilometers (0.75 miles) in diameter. It is the largest asteroid known to have passed closer than the Moon.[4] On 17 September 1918 the asteroid passed 0.00234 AU (350 thousand km; 0.91 LD) from Earth[3] with a peak apparent magnitude of around 8.4. The 1918 close approach distance is known with an accuracy of roughly ±120 km. The asteroid had come to opposition (opposite the Sun in the sky) on 9 August 1918 at magnitude 16.
2011 MD5 was not discovered until 30 June 2011,[1] when the asteroid was 1.3 AU (190 million km) from Earth. As of 2023, the asteroid has a 12-year observation arc and a well determined orbit.