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. The small near-Earth asteroids 2008 TC3, 2014 AA, 2018 LA, 2019 MO and 2022 EB5 are the only five asteroids discovered before impacting into Earth (see asteroid impact prediction). Scientists estimate that several dozen asteroids in the 6–12 m (20–39 ft) 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 384,400 km (238,900 mi), 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. (See also near-Earth asteroids and NEO Earth Close Approaches.)
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 36,000 km (22,000 mi), then its geocentric distance is 0.11 LD (approximately three times the width of the Earth).
The table shows that the years 2016 and 2017 had a total of 13 such close encounters that are known. Of these, eight were undetected until after they'd happened and only one was detected with more than 24 hours' notice. 2018 has fared better so far, with six out of the eight known close encounters being detected beforehand, albeit with less than 24 hours' notice in most cases.
This list does not include any of the hundreds of objects that collided with Earth, which were not discovered in advance, but were recorded by sensors designed to detect detonation of nuclear devices. Of the objects so detected, 78 had an impact energy greater than that of a 1-kiloton device (equivalent to 1,000 tons of TNT), including 11 which had an impact energy greater than that of a 10-kiloton device i.e. comparable to the atomic bombs used in the Second World War.[4]
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 100 m [330 ft] or more.) For comparison, the 1908 Tunguska event was caused by an object about 60–190 m (200–620 ft) in size, while the 2013 Chelyabinsk meteor which injured thousands of people and buildings when it generated a large airburst over Russia was estimated to be just 20 m (66 ft) across.
The table shows about 14 events in the 12 decades of 1900–2020 involving a body with an upper size estimate of 100 m (330 ft) or more making a close approach to Earth within one LD, with one (the Tunguska object) making impact.
Trajectory of the relatively large 2005 YU55 compared with the orbits of Earth and the Moon on 8–9 Nov 2011
The year 2011 was notable as two asteroids with size 100 m (330 ft) 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.[10] 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, in as much 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 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)
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.
^the asteroid is unconfirmed and will likely never receive a provisional designation.
^Distance error: 0.000420 AU, approach range: 0.016 to 0.25 LD. There was a roughly 2% chance of impact. The asteroid is most likely between 1 and 14 meters across, so would probably be detectable. The asteroid is unconfirmed and will likely never receive a provisional designation.
^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.
^S., Abe; J., Borovička; P., Spurný; P., Koten; Z., Ceplecha; Meteor Network Team in Japan (18–22 September 2006). "Earth-grazing fireball on March 29, 2006". European Planetary Science Congress 2006. Berlin. p. 486. Bibcode:2006epsc.conf..486A. Archived from the original on 28 May 2019. Retrieved 2015-03-14.
^Borovička, J.; Ceplecha, Z. (April 1992). "Earth-grazing fireball of October 13, 1990". Astronomy and Astrophysics. 257 (1): 323–328. Bibcode:1992A&A...257..323B. ISSN0004-6361.
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