Английская Википедия:2018 AH

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2018 AH is a sub-kilometer asteroid, classified as near-Earth object of the Apollo group, approximately Шаблон:Convert in diameter. It was first observed on 4 January 2018, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on Mauna Loa and quickly followed-up by many other surveys, with precovery observations found from Pan-STARRS and PTF from the day previous.

It is the largest known asteroid to pass so close to Earth (Шаблон:Convert) since Шаблон:Mpl in 1971,[1] and until Шаблон:Mpl- in 2028, although it was only discovered two days after its closest approach on 2 January 2018, at 04:25 UTC. The Tunguska asteroid was likely of a similar size, if not slightly smaller.

Before being recovered on 4 January 2022 11:49 UTC[2] at an Earth distance of 9.8 million km, the asteroid only had an observation arc of 46 days and had not been observed since February 2018. Being a short arc object that had not been observed for years generated an uncertainty that is relatively large. Between 24–31 December 2021 it was only known to make an Earth approach of between 1-8 million km.[3] As it came to perihelion on 3 December 2021, it was approaching from the direction of the Sun.

2021 close approach
Date JPL SBDB
nominal geocentric
distance 		uncertainty
region
(3-sigma)
2021-12-27.7 ± 3.6 days
(as known before recovery)		 4.5 million km ± 3.6 million km[3]
2021-12-27.548
(as known after recovery)		 4.68 million km ± 83 km[3]

Description

Шаблон:Mp has a fairly eccentric orbit, and its distance to the Sun therefore varies from as close as 90% of the Sun-Earth distance to over 4 times that distance. Due to this, among other factors, the asteroid remained undiscovered until its 2018 approach. It is almost always dimmer than magnitude 23, dimmer than most asteroid surveys can detect. During August–October 2013 it approached within ~0.3 AU of Earth and became as bright as magnitude 22.4, still rather dimmer than most survey-discovered asteroids, and it was not noticed.

2018 Approach

On its approach to Earth in 2018, Шаблон:Mp had recently passed perihelion and was moving outwards on its orbit. It therefore approached from roughly the direction of the Sun, where it was undetectable to ground-based optical observations. It reached its closest point to Earth at only 45 degrees from the Sun. It was discovered at a more observable elongation of 129 degrees and at a magnitude of 15.7, and was quickly followed up over the next several days due to its brightness. Шаблон:Mp remained brighter than magnitude 23 until late February 2018, and once more became mostly unobservable until its next Earth approach in December 2021.

Шаблон:Mp passed unusually close for such a bright asteroid, at an absolute magnitude of 22.5 (making it approximately 84–190 meters across).[1] The largest asteroid to pass so close to Earth in 2017 was only an absolute magnitude of 24.3 (or about 31–91 meters). Since 1900, the only asteroids larger than Шаблон:Mp known to pass closer than it to Earth are listed below:

Asteroid diameters marked in italics have had their size directly measured.

Designation Date Distance
(thousand km) 		H Diameter
(meters)
Tunguska asteroid 1908-06-30 Шаблон:Sort Шаблон:Sort 60–190
Шаблон:Mpl 1914-12-31 232.9 19.4 279–900
Шаблон:Mpl 1971-04-11 237.0 21.2 122–393
2018 AH 2018-01-02 297.0 22.5 84–190
Шаблон:Mpl 2028-06-26 248.7 18.3 921–943
99942 Apophis 2029-04-13 Шаблон:Sort 19.7 310–340
Шаблон:Mpl 2075-11-08 228.1 21.9 320–400
Шаблон:Mpl 2101-01-02 238.8 21.0 133–431
Шаблон:Mpl 2140-12-01 243.6 19.3 427–593
Шаблон:Mpl 2148-01-22 296.2 21.1 127–411

See also

References

Шаблон:Reflist

External links

Шаблон:2018 in space Шаблон:2021 in space Шаблон:Small Solar System bodies Шаблон:Authority control

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  1. ↑ 1,0 1,1 Ошибка цитирования Неверный тег <ref>; для сносок watchersnews не указан текст
  2. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MPEC2022-A26 не указан текст
  3. ↑ 3,0 3,1 3,2 Ошибка цитирования Неверный тег <ref>; для сносок Horizons2021 не указан текст
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