In February 2010, (308635) 2005 YU55 was rated 1 on the Torino Scale for a potential pass near Earth on 10 November 2103,[12] that posed no unusual level of danger.

[15] During the close approach the asteroid reached about apparent magnitude 11,[6][16] and would have been visible to experienced observers using high-end binoculars with an objective lens of 80+ mm if it were not for bright moonlight preventing a true dark sky.

Since the gibbous moon did interfere with the viewing,[3] observers trying to visually locate the asteroid required a telescope with an aperture of 6 inches (15 centimeters) or larger.

[18] According to Jay Melosh, if an asteroid the size of (308635) 2005 YU55 (~400 m across) were to hit land, it would create a crater 6.3 km (3.9 mi) across, 518 m (1,699 ft) deep and generate a seven-magnitude-equivalent-earthquake.

Although radar measurements do not detect visible light they can determine the distance and size of an object with a high degree of accuracy.

[21] On 11 November 2011, higher-resolution images showed concavities, a ridge near the asteroid's equator, and numerous features interpreted as decameter-scale boulders.

A 150–200 meter-long, ~20 meter-high rise forms a portion of the ridge-line, and the number of boulders on the surface is comparable to that seen on the asteroid 25143 Itokawa by the Hayabusa spacecraft.