In 2012, Thomas G. Müller et al. studied Ryugu using a variety of observatories, and suggested that the asteroid is "almost spherical", a fact that hinders precise conclusions, with retrograde rotation, an effective diameter of 0.85–0.88 kilometers, and a geometric albedo of 0.044 to 0.050. They estimated that the grain sizes of its surface materials are between 1 and 10 mm.[3]