2019 OK

The first detection made public occurred on 24 July 2019, when it was {{convert|0.01|AU|km mi|abbr=on}} from Earth and had an apparent magnitude of 14.7. The full moon on 16 July 2019 slowed down the asteroid discovery rate during mid-July. The asteroid was detected by Cristóvão Jacques, Eduardo Pimentel and João Ribeiro at the private SONEAR Observatory in Oliveira, Minas Gerais when it was very close to opposition (opposite the Sun in the sky) with a solar elongation of 170 degrees. About 10 hours later it was independently detected by ASAS-SN project in images from two of its telescopes, which allowed a preliminary determination of its orbit. It was subsequently listed on the Minor Planet Center's Near-Earth Object Confirmation Page (NEOCP) as S511618. The listing was confirmed and publicly announced as 2019 OK with three hours remaining before the 25 July 2019 closest approach.

Various circumstances prevented an earlier discovery, despite the efforts to continuously hunt for such objects. The last previous appearance was not lost in the glare of the Sun, but was not favorable to survey instruments located in the Northern Hemisphere, due to its celestial direction in the Southern constellation Capricornus and close to the bright moon. The Pan-STARRS1 telescope did record an image of 2019 OK on 28 June 2019 when it was {{convert|0.39|AU|km mi|abbr=on}} from Earth and had an apparent magnitude of 22.9. Automatic analysis missed detecting the object in the Pan-STARRS image because the object was too faint. The Pan-STARRS1 telescope again saw the object on 7 July 2019 when the object was brighter with magnitude 21.2. However, it was at that time moving directly towards the observer and its apparent motion across the sky was extremely slow, with a rate of 0.01 degrees/day, and it was not recognized as a moving object.

The asteroid is a member of the Flora family ({{small|402}}), a populous asteroid family and the largest family of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 0.5–3.4 AU once every 2 years and 9 months (993 days; semi-major axis of 1.95 AU). Its orbit has an eccentricity of 0.76 and an inclination of 1° with respect to the ecliptic. After evaluating its orbit, the asteroid was identified as the most probable parent body of the particles responsible for the meteor shower designated, 17 Capricornids (SCP #1042).

On 25 July 2019 at 01:22 UTC it had its closest approach to Earth, when it passed about {{convert|0.00047697|AU|km mi|abbr=on}}—less than one-fifth of the distance to the Moon. Its speed was nearly {{convert|88,500|km|mi}} per hour.{{Cite web |url=http://www.astronomy.com/news/2019/07/a-large-asteroid-just-zipped-between-earth-and-the-moon |title=A large asteroid just zipped between Earth and the Moon |last=Haynes |first=Korey |website=astronomy.com |access-date=2019-07-26}}{{cite news |last1=Chiu |first1=Allyson |title='It snuck up on us': Scientists stunned by 'city-killer' asteroid that just missed Earth |url=https://www.washingtonpost.com/nation/2019/07/26/it-snuck-up-us-city-killer-asteroid-just-missed-earth-scientists-almost-didnt-detect-it-time/ |newspaper=The Washington Post |accessdate=27 July 2019 |date=July 26, 2019}}

{{multiple image

| align = left

| direction = horizontal

| width = 300

| header = Animation of 2019 OK's orbit

| image1 = Animation of 2019 OK orbit around Sun.gif

| caption1 = Around the Sun

| image2 = Animation of 2019 OK orbit around Earth.gif

| caption2 = Around the Earth

| footer =
{{legend2|magenta| 2019 OK }}{{·}}{{legend2|Yellow|Sun}}{{·}}{{legend2|Cyan|Mercury}}{{·}}{{legend2| Lime |Venus }}{{·}}{{legend2|Royalblue|Earth}} {{·}}{{legend2|gold|Moon}} }}

{{clear}}

On 28 July 2116 the asteroid will pass about {{convert|0.03|AU|km mi|abbr=on}} from Earth.

Asteroids in the {{convert|20|m|ft|abbr=on}} Chelyabinsk meteor size range to {{convert|50|m|ft|abbr=on}} Tunguska size range (absolute magnitude H ~26–24) approach closer than the Moon about once per month. Asteroids with an absolute magnitude of 26–24 will vary in size from {{convert|17|to|94|m|ft|abbr=on}} depends on the objects albedo (how reflective it is).[https://cneos.jpl.nasa.gov/tools/ast_size_est.html Asteroid Size Estimator] using H=26 albedo=0.25 and H=24 albedo=0.05

If 2019 OK is around {{convert|100|m|ft|abbr=on}} in diameter, an Earth impact could have released as much power as the 50 megatons generated by the Tsar Bomba hydrogen bomb.[http://www.esa.int/spaceinimages/Images/2018/06/Asteroid_danger_explained Asteroid Danger Explained] (ESA) If 2019 OK is around the middle of the size estimates, it could instead have released the equivalent explosive energy of about 10 megatons of TNT similar to the 1908 Tunguska event that flattened 2,000 km² (770 square miles) of forest land. If 2019 OK is on the smaller size it still could have released over 30 times the energy of the atomic blast by Little Boy at Hiroshima.[https://www.smh.com.au/national/earth-had-a-near-miss-with-city-killer-asteroid-this-morning-20190725-p52apn.html The day Earth had a near-miss with a 'city-killer' asteroid.] Liam Mannix, The Sydney Herald 25 July 2019.

• 2020 LD
• Asteroid impact prediction
• List of asteroid close approaches to Earth in 2019
• List of asteroid close approaches to Earth
• List of bolides (asteroids and meteoroids that impacted Earth)

{{notelist}}

{{reflist|30em|refs=

{{cite web

|type = 2019-07-25 last obs.

|title = JPL Small-Body Database Browser: (2019 OK)

|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=3843336;cad=1

|publisher = Jet Propulsion Laboratory

|accessdate = 28 July 2019}}

{{cite web

|title = 2019 OK

|work = Minor Planet Center

|url = https://www.minorplanetcenter.net/db_search/show_object?object_id=2019+OK

|accessdate = 28 July 2019}}

{{cite web

|title = MPEC 2019-O56 : 2019 OK

|publisher = IAU Minor Planet Center

|date = 25 June 2019

|url = https://minorplanetcenter.net/mpec/K19/K19O56.html

|accessdate = 31 July 2019}} (K19O00K)

{{cite web

|first1 = Bill |last1 = Gray

|title = Pseudo-MPEC for 2019 OK = S511618 = asassn3

|url = https://projectpluto.com/temp/2019ok.htm

|website = Project Pluto

|accessdate = 1 August 2019}}

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|bibcode = 2015aste.book..297N

|doi = 10.2458/azu_uapress_9780816532131-ch016

|arxiv = 1502.01628

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{{cite journal

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|last5 = Silva

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|title = Identification of new meteor showers SCP (#1042) and OSG (#1043) and their associations with the asteroids 2019 OK and 2017 NT5

|journal = EMeteorNews

|date = May 2021

|volume = 6

|issue = 4

|pages = 297–310

|url = https://downloads.meteornews.net/ezine/eMetN2021_4.pdf

|access-date = 30 June 2021

|archive-date = 26 May 2021

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{{cite journal

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|journal = Icarus

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|publisher = Academic Press

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|doi = 10.1016/J.ICARUS.2021.114735

|doi-access= free

}}

}}

• {{NeoDys|2019+OK}}
• {{MPC|2019+OK|2019 OK}} at the IAU Minor Planet Center
• {{JPL small body|id=3843336}}

{{2019 in space}}

{{Authority control}}

{{DEFAULTSORT:2019 OK}}

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Category:Minor planet object articles (unnumbered)

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