2021 GW4 is an Apollonear-Earth object roughly 5 meters (20 feet) in diameter. It was discovered by the Mount Lemmon Survey on 8 April 2021.[1] On 12 April 2021 13:01 UTC it passed 19821km from the surface of Earth.[3] The uncertainty in the close approach distance was ±30 km.[4]
The Earth approach caused the asteroid to migrate inward and reduced the orbital period by roughly 71 days (from 678 days to 607 days).[5] As a result of the orbit change, it came to its next perihelion (closest approach to the Sun) on 6 May 2021.
Meteor scientist Peter Brown[6] and astronomers Jonathan McDowell[7] and Michael Busch[8] agree that the fireball near South Florida at 13 April 2021 2:16 UTC was unrelated to 2021 GW4. The unrelated fireball became visible at 100 kilometers (62 mi) above sea level and airburst at 37 kilometers (23 mi) before entering dark flight and landing in the Atlantic ocean.[6] Thousands of fireballs occur every day.[9]
^Horizons output. "Orbital Elements for Asteroid (2021 GW4)". Retrieved 17 April 2021. ("Ephemeris Type" select "Orbital Elements" · "Center" should already be set for "Sun (body center)" (aka @sun) · "Time Span" I selected "2020-Dec-17" to match the current JPL SBDB numbers and "2021-Jun-17" with a step size of 6 months.)
