1. Ten lunar distances:  A "lunar distance" (LD) is the average distance between Earth and Moon (about 384,400 km.). Ten lunar distances has no special astronomical importance but is a useful arbitrary "bubble" within which to organize this report. An approach by a small Solar-System body starts to become interesting at less than four LD out from Earth as it encounters our planet's "Hill sphere" (distance indicated by the blue line in this illustration at about 3.9 LD). This is a region where the Earth exercises gravitational influence over passing objects and can change their orbital paths. The Moon also has a Hill sphere, outlined here as a gray circle. (The Earth and Moon are not shown to scale.)

2. Data credit:  All data on this page derived from orbit solutions comes from the NASA JPL Solar System Dynamics (SSD) Group through its Horizons system. All information about optical observations comes from the IAU Minor Planet Center (MPC) and info about radar observations comes from JPL SSD. NASA, JPL, and the MPC are not associated with this page or A/CC, and responsibility for the interpretation of this information and its use here rests entirely with A/CC. Important note: Approach times presented here as to-the-minute may have unstated uncertainties of a few minutes, or many minutes or even hours for objects with old or very short observation spans, which is significant because the Earth moves through its own diameter in about six minutes. Thus actual encounter distances may vary, occasionally by as much as ten lunar distances. See JPL's Close Approach Tables for nominal vs. minimum possible passage distances and times and for their note about uncertainties.

3. Size estimates:  Object diameters are rough approximations derived by standard formula from H, an object's "absolute magnitude" (brightness), where higher numbers represent dimmer (thus usually smaller) objects.