[3] Megaira is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.
[3] In the Tholen classification-SMASS classification, Megaira is closest to a dark F-type asteroid, and somewhat similar to an X-type, though with an unusual (U) and noisy spectra (:).
Lightcurve analysis gave a well-defined rotation period of 12.879±0.001 hours with a brightness variation of 0.12±0.01 magnitude (U=3).
[11][12][13] According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Megaira measures between 55.09 and 85.50 kilometers in diameter and its surface has an albedo between 0.03 and 0.06.
[6][7][8][9][14] The Collaborative Asteroid Lightcurve Link takes an albedo of 0.0469 from Petr Pravec's revised WISE data and calculates a diameter of 78.29 kilometers based on an absolute magnitude of 9.47.