This is a list of examples where an asteroid or meteoroid travels close to the Earth. Some are regarded as potentially hazardous objects if they are estimated to be large enough to cause regional devastation.
Near-Earth object detection technology began to improve around 1998, so objects being detected as of 2004 could have been missed only a decade earlier due to a lack of dedicated near-Earth astronomical surveys. As sky surveys improve, smaller and smaller asteroids are regularly being discovered. Scientists estimate that several dozen asteroids in the 6–12m (20–39ft) size range fly by Earth at a distance closer than the moon every year, but only a fraction of these are actually detected.[1][2] See also lists dedicated to specific years such as List of asteroid close approaches to Earth in 2023.
Timeline of approaches within one lunar distance
The average distance to the Moon (or lunar distance (LD)) is about 384,400km (238,900mi), which is around 30 times the diameter of the Earth.[3] Below are lists of close approaches less than one LD for a given year.
These statistics are based on the close approach database of the Center for Near-Earth Object Studies (CNEOS).[4] 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 statistics below only include close approaches that are evidenced by observations, thus the pre-discovery close approaches are only included if the object was found by precovery. These statistics and relevant databases do not consider impacts as close approaches, be them [List of predicted asteroid impacts on Earth|predicted impacts on Earth]] that burned up in its atmosphere, or more objects that collided with Earth's atmosphere without prior detection in space.
Discovered > 1 year in advance Discovered > 7 weeks in advance Discovered > 1 week in advance Discovered up to 1 week in advance < 24 hours' warning < no warning
From the list in the first section, these are the closest known asteroids per year that approach Earth within one lunar distance. More than one asteroid per year may be listed if its geocentric distance[note 1] is within a tenth of the lunar distance, or 0.10 LD. For comparison, since a satellite in a geostationary orbit has an altitude of about 36,000km (22,000mi), then its geocentric distance is 0.11 LD (approximately three times the width of the Earth).
The CNEOS database of close approaches lists some close approaches a full orbit or more before or after the discovery of the object, derived by orbit calculation. Until 2001 and in future years, all of these close approaches are included in the list below, but from the start of regular discoveries each year in 2001 until the current year, the list is limited to close approaches that are evidenced by observations, thus any of these pre-discovery close approaches are only included if the object was found by precovery.
This list and relevant databases do not consider impacts as close approaches, thus this list does not include any of the hundreds of objects that collided with Earth's atmosphere which were not discovered in advance but were observed visually or recorded by sensors designed to detect detonation of nuclear devices.[5]
Rows highlighted red indicate objects which were not discovered until after closest approach
Rows highlighted yellow indicate objects discovered less than 24 hours before closest approach
Rows left white indicate objects discovered 1–7 days before closest approach
Rows highlighted green indicate objects discovered more than one week before closest approach
Rows highlighted blue indicate objects discovered more than one year before closest approach, i.e. objects successfully cataloged on a previous orbit, rather than being detected during final approach.
A notable case is the relatively large asteroid Duende, which was predicted nearly a year in advance, coincidentally approaching just a few hours after the unrelated Chelyabinsk meteor, which was unpredicted, but injured thousands of people when it impacted.
Largest per year
From the lists in the first section, these are the largest known asteroids per year that approach Earth within one LD. (More than one asteroid per year may be listed if its size is 100m[330ft] or more.) For comparison, the 1908 Tunguska event was caused by an object about 60–190m (200–620ft) in size, while the 2013 Chelyabinsk meteor, which injured thousands of people and damaged buildings when it generated a large airburst over Russia, was estimated to be just 20m (66ft) across.
Trajectory of the relatively large 2005 YU55 compared with the orbits of Earth and the Moon on 8–9 Nov 2011
The CNEOS database of close approaches lists some close approaches a full orbit or more before or after the discovery of the object, derived by orbit calculation. Until 2001 and in future years, all of these close approaches were considered for the list below, but from the start of regular discoveries each year in 2001 until the current year, the list is limited to close approaches that are evidenced by observations, thus any of these pre-discovery close approaches are only included if the object was found by precovery.
The year 2011 was notable as two asteroids with size 100m (330ft) or more approached within one lunar distance.
Fastest per year
The average near-Earth asteroid, such as 2019 VF5, passes Earth at 18 km/s. The average short-period comet passes Earth at 30 km/s, and the average long-period comet passes Earth at 53 km/s.[8] A retrograde parabolic Oort cloud comet (e=1, i=180°) could pass Earth at 72 km/s when 1 AU from the Sun.
Fastest asteroid within 1 LD for each year (these asteroids have eccentric orbits)
Objects which enter and then leave Earth's atmosphere, the so-called Earth-grazers, are a distinct phenomenon, inasmuch as entering the lower atmosphere can constitute an impact event rather than a close pass. Earth-grazer can also be short for a body that "grazes" the orbit of the Earth, in a different context.
Animation of the 2015 TB145 (NEO) flyby, as seen from the center of the Earth, with hourly trace circles along the path of motion
Overview
Diagram showing spacecraft and notable asteroids (past and future) between the Earth and the Moon.
Plot of orbits of known Potentially Hazardous Asteroids (size over 140m[460ft] and passing within 7.6millionkm[4.7millionmi] of Earth's orbit) as of early 2013 (alternate image)
Notes
↑ Distance from the center of Earth to the center of the object. See the NASA/JPL Solar System Dynamics Glossary: GeocentricArchived 2013-02-14 at the Wayback Machine . Earth has a radius of approximately 6,400 km.
↑ Ceplecha, Z. (March 1994). "Earth-grazing daylight fireball of August 10, 1972". Astronomy and Astrophysics. 283 (1): 287–288. Bibcode:1994A&A...283..287C. ISSN0004-6361.
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![Plot of orbits of known Potentially Hazardous Asteroids (size over 140 m [460 ft] and passing within 7.6 million km [4.7 million mi] of Earth's orbit) as of early 2013 (alternate image) Potentially Hazardous Asteroids 2013.png](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f6/Potentially_Hazardous_Asteroids_2013.png/550px-Potentially_Hazardous_Asteroids_2013.png)
