2018 AH
   HOME

TheInfoList



OR:

2018 AH is a sub-kilometer
asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
, classified as
near-Earth object A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...
of the
Apollo group Apollo Education Group, Inc. is an American corporation based in the South Phoenix area of Phoenix, Arizona, with an additional corporate office in Chicago, Illinois. It is privately-owned by a consortium of investors including The Vistria Grou ...
, approximately in diameter. It was first observed on 4 January 2018, by the
Asteroid Terrestrial-impact Last Alert System The Asteroid Terrestrial-impact Last Alert System (ATLAS) is a robotic astronomical survey and early warning system optimized for detecting smaller near-Earth objects a few weeks to days before they Impact event, impact Earth. Funded by NASA, an ...
(ATLAS) on
Mauna Loa Mauna Loa (, ; ) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean. Mauna Loa is Earth's largest active volcano by both mass and volume. It was historically considered to be the largest ...
and quickly followed-up by many other surveys, with
precovery In astronomy, precovery (short for pre-discovery recovery) is the process of finding the image of a celestial object in images or photographic plates predating its discovery, typically for the purpose of calculating a more accurate orbit. This ha ...
observations found from
Pan-STARRS The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1; List of observatory codes, obs. code: IAU code#F51, F51 and Pan-STARRS2 obs. code: IAU code#F52, F52) located at Haleakala Observatory, Hawaii, US, consists of astronomical ...
and PTF from the day previous. It is the largest known asteroid to pass so close to Earth () since in 1971, and until 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 at an Earth distance of 9.8 million km, the asteroid only had an
observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...
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. As it came to perihelion on 3 December 2021, it was approaching from the direction of the Sun.


Description

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 Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...
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, had recently passed
perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
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. remained brighter than magnitude 23 until late February 2018, and once more became mostly unobservable until its next Earth approach in December 2021. passed unusually close for such a bright asteroid, at an absolute magnitude of 22.5 (making it approximately 84–190 meters across). 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 known to pass closer than it to Earth are listed below: Asteroid diameters marked in ''italics'' have had their size directly measured.


See also

* – Short arc object (not recently observed) approaching in January 2022 * – Short arc object (not recently observed) possibly approaching in May 2022 * List of asteroid close approaches to Earth in 2018


References


External links


MPEC 2018-A23 : 2018 AH
''
Minor Planet Electronic Circular The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function ...
'', 6 January 2018
Tweet about asteroid 2018 AH
''Minor Planet Center'' * * {{DEFAULTSORT:2018 AH # Minor planet object articles (unnumbered) Discoveries by ATLAS 20180102 20211227 20180104