| Year Mass Notes | |
| 1931 1 Earth Nicholson & Mayall | |
| 1942 0.91 Earth Wylie | |
| 1948 0.1 (1/10 Earth) Kuiper | |
| 1973 0.025 (1/40 Earth) Rawlins | |
| 1976 0.01 (1/100 Earth) Cruikshank, Pilcher, & Morrison | |
| 1978 0.002 (1/500 Earth) Christy & Harrington | |
| 2006 0.00218 (1/459 Earth) Buie et al. | |