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.
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. (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 36,000km (22,000mi), 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 detonated on Hiroshima and Nagasaki 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 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.
The table shows about 14 events in the decades 1900–2020 involving a body with an upper size estimate of 100m (330ft) 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 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.[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, 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.
↑ 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.
Related Research Articles
A near-Earth object (NEO) is any small Solar System body orbiting the Sun which has a closest approach to the Sun (perihelion) that is less than 1.3 times the Earth–Sun distance. This definition applies to the object's orbit around the Sun, rather than its current position, thus an object with such an orbit is considered a NEO even at times when it is far from making a close approach of Earth. If a NEO's orbit crosses the Earth's orbit, and the object is larger than 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but about 0.35% are comets.
A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of impact. They are conventionally defined as having a minimum orbit intersection distance with Earth of less than 0.05 astronomical units and an absolute magnitude of 22 or brighter, the latter of which roughly corresponds to a size larger than 140 meters. More than 99% of the known potentially hazardous objects are no impact threat over the next 100 years. As of September 2022, just 17 of the known potentially hazardous objects listed on the Sentry Risk Table could not be excluded as potential threats over the next hundred years. Over hundreds if not thousands of years though, the orbits of some "potentially hazardous" asteroids can evolve to live up to their namesake.
(308635) 2005 YU55, provisionally named 2005 YU55, is a potentially hazardous asteroid 360±40 meters in diameter, as measured after its Earth flyby. Previously it was estimated to be 310 meters or about 400 m (1,300 feet) in diameter. It was discovered on 28 December 2005 by Robert S. McMillan at Steward Observatory, Kitt Peak. On 8 November 2011 it passed 0.85 lunar distances (324,900 kilometers; 201,900 miles) from Earth.
2014 HQ124 is a sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Aten group, approximately 400 meters (1,300 feet) in diameter. It passed 3.25 lunar distances (LD) from Earth on 8 June 2014. It was discovered on 23 April 2014 by NEOWISE. It is estimated that an impact event would have had the energy equivalent of 2,000 megatons of TNT and would have created a 5 km (3 mi) impact crater. The news media misleadingly nicknamed it The Beast. 2014 HQ124 previously passed this close to Earth in 1952 and will not again until at least 2307. Radar imaging suggests it may be a contact binary.
2013 TX68 is an Apollo asteroid and near-Earth object discovered on 6 October 2013 by the Catalina Sky Survey, during which it was near a close approach of 5.4 Lunar distances (LD) from the Earth. The asteroid only has a 10-day observation arc which makes long-term predictions of its position less certain. It was observed for three days as it approached Earth in the night sky starting with the sixth of October, 2013. Then it became unobservable by being between the Earth and the Sun, then not recovered due to its small size and dimness. Precovery images by Pan-STARRS from 29 September 2013 were announced on 11 February 2016 that extended the observation arc to 10 days. It was removed from the Sentry Risk Table on 11 February 2016, so there is no risk of impact from this object for the next hundred years or more. The asteroid was last observed on 9 October 2013.
2018 GE3 is a sub-kilometer asteroid on a highly eccentric orbit, classified as a near-Earth object of the Apollo group, approximately 48–110 meters (160–360 feet) in diameter. It was first observed on 14 April 2018, by astronomers with the Catalina Sky Survey one day prior to its sub-lunar close encounter with Earth at 0.5 lunar distance. It is one of the largest known asteroids (possibly the largest) in observational history to ever pass that close to Earth (also see list).
(164121) 2003 YT1, provisional designation 2003 YT1, is a bright asteroid and synchronous binary system on a highly eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 2 kilometers (1.2 miles) in diameter. It was discovered on 18 December 2003, by astronomers with the Catalina Sky Survey at the Catalina Station near Tucson, Arizona, in the United States. The V-type asteroid has a short rotation period of 2.3 hours. Its 210-meter sized minor-planet moon was discovered at Arecibo Observatory in May 2004.
(231937) 2001 FO32 is a near-Earth asteroid classified as a potentially hazardous asteroid of the Apollo group. With an estimated diameter around 550 m (1,800 ft), it was discovered by the Lincoln Near-Earth Asteroid Research at Socorro, New Mexico on 23 March 2001. The asteroid safely passed by Earth on 21 March 2021 16:03 UTC from a closest approach distance of 0.0135 AU (2.02 million km; 1.25 million mi), or 5.25 lunar distances (LD). During the day before closest approach, 2001 FO32 reached a peak apparent magnitude of 11.7 and was visible to ground-based observers with telescope apertures of at least 20 cm (8 in). It is the largest and one of the fastest asteroids to approach Earth within 10 LD (3.8 million km; 2.4 million mi) in 2021.
↑ 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)
