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List of asteroid close approaches to Earth in 2018
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Below is the list of asteroid close approaches to Earth in 2018.
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Timeline of known close approaches less than one lunar distance from Earth
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A list of known near-Earth asteroid close approaches less than 1 lunar distance (0.0025696 AU (384,410 km; 238,860 mi)) from Earth in 2018, based on the close approach database of the Center for Near-Earth Object Studies (CNEOS).[1]
For reference, the radius of Earth is approximately 0.0000426 AU (6,370 km; 3,960 mi) or 0.0166 lunar distances.
Geosynchronous satellites have an orbit with semi-major axis length of 0.000282 AU (42,200 km; 26,200 mi) or 0.110 lunar distances. Five asteroids (2018 BD, 2018 PD20, 2018 UA, 2018 WG, and 2018 WV1) are confirmed to have passed within this distance, and unconfirmed or confirmed but poorly observed asteroids A106fgF, A107j4q, ZB0A262, 2018 DN4, ZGBE54F, A1080DC 2018 VQ10, ZW87F01, and ZW900BE may have also passed within this distance.
The largest asteroid to pass within 1 LD of Earth in 2018 was 2018 AH with an estimated diameter of around 137 meters and an absolute magnitude of 22.5. The fastest asteroid to pass within 1 LD of Earth in 2018 was 2018 GE3 that passed Earth with a velocity with respect to Earth of 29.6 km/s (66,000 mph).[2][note 1]
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 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 2018 LA, an asteroid which was predicted to impact on Earth and burned up in its atmosphere, as well as several more objects that collided with Earth's atmosphere in 2018 which weren't discovered in advance, but were observed visually or recorded by sensors designed to detect detonation of nuclear devices.[3]
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 highlighted green indicate objects discovered more than one week before closest approach
Rows highlighted turquoise indicate objects discovered more than 7 weeks 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)
In addition to the confirmed asteroids on the above list, which feature in the CNEOS close approach database, there have been well-observed unconfirmed or confirmed but poorly observed objects with a 50% or greater chance of passing within 1 LD of the Earth, which are listed separately below.
Warning times by size
This sub-section visualises the warning times of the close approaches listed in the table of confirmed close approaches, depending on the size of the asteroid. The sizes of the charts show the relative sizes of the asteroids to scale. For comparison, the approximate size of a person is also shown. This is based the absolute magnitude of each asteroid, an approximate measure of size based on brightness.
Absolute magnitude H ≥ 30 (smallest)
(size of a person for comparison)
Absolute magnitude 30 > H ≥ 29
Absolute magnitude 29 > H ≥ 28
Absolute magnitude 28 > H ≥ 27
Absolute magnitude 27 > H ≥ 26
Absolute magnitude 26 > H ≥ 25
Absolute magnitude 25 > H (largest)
- After closest approach: 1 (25.0%)
- < 24 hours before: 0 (0.0%)
- up to 7 days before: 2 (50.0%)
- > one week before: 0 (0.0%)
- > 7 weeks before: 0 (0.0%)
- > one year before: 1 (25.0%)
Notes
- 2018 GE3 passed Earth with a velocity with respect to Earth of 29.6 km/s and was approaching the Sun at 35.9 km/s.
- Distance from the center of Earth to the center of the object. See the NASA/JPL Solar System Dynamics Glossary: Geocentric. Earth has a radius of approximately 6,400 km.
- 0.00141+0.00156
−0.00137 AU, approach range: 0.018 to 1.157 LD. There is no chance that it impacted Earth, as the minimum distance (0.018 LD) is still roughly 410 kilometers above Earth's surface. - A perigee during the asteroid's capture as temporary satellite by Earth
- distance error: 0.0000107 AU, approach range: 0 to 0.0052 LD. Assuming the observations were not made in error, there was a (~9%) this asteroid hit the Earth (Impact path). However, there was no record of an impact reported, so if it did indeed impact Earth, it was likely in an uninhabited region or in the Pacific ocean. (The further west in the impact path, the larger the asteroid would be. If it hit west of Africa or in the Indian ocean, it would have been several meters across and have been recorded.) The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000305 AU, approach range: 0.037 to 0.27 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000347 AU, approach range: 0.047 to 0.32 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.00000608 AU, approach range: 0.078 to 0.082 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000184 AU, approach range: 0.13 to 0.28 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000296 AU, approach range: 0.40 to 0.63 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.0000651 AU, approach range: 0.085 to 0.136 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000600 AU, approach range: 0.43 to 0.89 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.0000181 AU, approach range: 0.100 to 0.115 LD.
- distance error: 0.0000114 AU, approach range: 0.325 to 0.333 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000583 AU, approach range: 0.017 to 0.46 LD. The asteroid is unconfirmed and will likely never receive a provisional designation. There is no chance of impact as the asteroid was discovered after its closest approach.
- distance error: 0.000165 AU, approach range: 0.023 to 0.152 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
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Timeline of close approaches less than one lunar distance from the Moon
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The number of asteroids listed here are significantly less than those of asteroids that approach Earth for several reasons. Asteroids that approach Earth not only move faster, but are brighter and are easier to detect with modern surveys because:
- Asteroids that come closer to Earth are a higher priority to confirm, and only confirmed asteroids are listed with a lunocentric approach distance.
- Those that closely approach the Moon are frequently lost in its glare, making them harder to confirm. They are similarly hard to discover during the new moon, when the Moon is too close to the Sun to detect asteroids while they are near the Moon.
These factors severely limit the amount of Moon-approaching asteroids, to a level many times lower than the asteroids detected passing as close to Earth.
Notes
- distance error: 0.000633 AU, approach range: 0.33 to 0.82 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- 0.00128+0.00123
−0.000241 AU. Approach range: 0.41 to 0.98 LD. - distance error: 0.00000167 AU, approach range: 0.9942 to 0.9955 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000198 AU, approach range: 0.73 to 0.89 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000194 AU, approach range: 0.58 to 0.73 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: Unknown, Approach range: Unknown. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000390 AU, approach range: 0.42 to 0.72 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.000506 AU, approach range: 0.56 to 0.95 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.0000329 AU, approach range: 0.943 to 0.968 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
- distance error: 0.0000552 AU, approach range: 0.972 to 1.015 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
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Additional examples
An example list of near-Earth asteroids that passed more than 1 lunar distance (384,400 km or 0.00256 AU) from Earth in 2018.
Statistics
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Virtual Impactors
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List of asteroids that are listed on the Sentry Risk Table because they have short observation arcs with poorly constrained orbits and have a chance of impacting Earth in 2018. Given a short observation arc, many different orbits fit the observed data. These objects could be millions if not billions of kilometers from Earth on the date of a low probability virtual impactor. For example, 2005 TM173 is expected to be 5 AU (700 million km) from Earth in December 2018 around the time of the 3 virtual impactors.[6] 2010 GZ60 was removed from the sentry table in February 2018 after further observations were found by NEOWISE, ruling out any possible impacts.
Cumulatively among the asteroids listed below, there is a roughly 1 in 98,700 chance that any of the asteroids will impact Earth in 2018. Most of this comes from asteroid 2008 US which is only ~2 meters in diameter and had a 1 in 240,000 chance of impact on 18 April 2018.
Also included are asteroids discovered before impact (specifically, 2018 LA) and exceptionally massive fireballs with either an equivalent yield of more than 1 kiloton of TNT or an estimated size of more than 3 meters.
Notes
- This is a measurement of how far off of the "best fit" orbit the asteroid would have to have for it to hit at this time. Further values from 0 mean that the measured positions of the asteroid used to calculate its orbit would need to be highly inaccurate for it to hit Earth. For reference, 1.0/-1.0=31.7% odds the observations would be this inaccurate, 2.0/-2.0=4.6% odds, 3.0/-3.0=0.27% odds.
- 2011 CF66 has a cumulative probability of 1 in 38,900,000 (Palermo scale -7.16) of impacting Earth in 2018.
- 2008 EL68 has a cumulative probability of 1 in 1,200,000 (Palermo scale -5.81) of impacting Earth in 2018.
- 2009 VZ39 has a cumulative probability of 1 in 13,600,000 (Palermo scale -6.89) of impacting earth in 2018.
- 2015 HV182 has a cumulative probability of 1 in 239,000,000 (Palermo scale -5.10) of impacting Earth in 2018.
- 2008 EM68 has a cumulative probability of 1 in 3,100,000 (Palermo scale -6.04) of impacting Earth in 2018.
- 2014 HG196 has a cumulative probability of 1 in 268,000,000 (Palermo scale -7.64) of impacting Earth in 2018.
- 2016 AZ193 has a cumulative probability of 1 in 61,300,000 (Palermo scale -6.76) of impacting Earth in 2018.
- 2008 VS4 has a cumulative probability of 1 in 339,000,000 (Palermo scale -6.54) of impacting Earth in 2018.
- 2014 LY21 has a cumulative probability of 1 in 384,000 (Palermo scale -5.53) of impacting Earth in 2018.
- 2014 HR197 has a cumulative probability of 1 in 385,000,000 (Palermo scale -7.74) of impacting Earth in 2018.
- 2010 VP139 has a cumulative probability of 1 in 54,000,000 (Palermo scale -8.24) of impacting earth in 2018.
- 2005 TM173 has a cumulative probability of 1 in 336,000,000 (Palermo scale -6.50) of impacting earth in 2018.
- 2014 JT79 has a cumulative probability of 1 in 46,300,000 (Palermo scale -7.08) of impacting Earth in 2018.
- 2010 GZ60 was ruled out as a potential impactor after another observation was found by NEOWISE, improving the orbit enough to determine that it is not a near-earth object
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See also
- List of asteroid close approaches to Earth
- List of asteroid close approaches to Earth in 2017
- List of asteroid close approaches to Earth in 2019
- List of bolides (asteroids and meteoroids that impacted Earth)
- Asteroid impact prediction
References
External links
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