Asteroids which came closer to Earth than the Moon in 2021 by time of discovery
Asteroids which came closer to Earth than the Moon in 2021 by discoverer
Prediction accuracy for asteroids of magnitude 27 or larger predicted to pass within 1 lunar distance of Earth in 2021
Below is the list of asteroids that have come close to Earth in 2021.
Timeline of known close approaches less than one lunar distance from Earth
A list of known near-Earth asteroid close approaches less than 1 lunar distance () from Earth in 2021, based on the close approach database of the Center for Near-Earth Object Studies (CNEOS).
For reference, the radius of Earth is about or 0.0166 lunar distances. Geosynchronous satellites have an orbit with semi-major axis length of or 0.110 lunar distances.
The largest asteroid to pass within 1 LD of Earth in 2021 was with an estimated diameter of around 68 meters and an absolute magnitude of 24.0. The fastest asteroid to pass within 1 LD of Earth in 2021 was that passed Earth with a velocity with respect to Earth of . passed Earth with a velocity with respect to Earth of 27.7 km/s and was moving away from the Sun at 37.0 km/s.
The CNEOS database of close approaches lists some close approaches a full orbit or more before the discovery of the object, derived by orbit calculation. The list below only includes close approaches that are evidenced by observations, thus the pre-discovery close approaches would only be included if the object was found by precovery, but there was no such close approach in 2021.
This list and the relevant databases do not consider impacts as close approaches, thus this list does not include any of the objects that collided with Earth's atmosphere in 2021, none of which were discovered in advance, but were observed visually or recorded by sensors designed to detect detonation of nuclear devices.