View source for 2022 WJ1

{{short description|Meteoroid that impacted near Ontario, Canada in November 2022}}
{{DISPLAYTITLE:{{mp|2022 WJ|1}}}}
{{Use dmy dates|date=November 2022}}
{{Infobox planet
 | minorplanet     = yes
 | name            = {{mp|2022 WJ|1}}
 | background      = #FFC2E0
 | image           = 2022 WJ1-orbit.png
 | image_scale      =
 | caption         = Orbit before impact
 | discovery_ref   = <ref name="MPC-object" /><ref name="MPEC-2022-W69"/>
 | discoverer      = David Rankin<br/>([[Mount Lemmon Survey|Mt. Lemmon Srvy]])
 | discovery_site  = [[Mount Lemmon Observatory|Mt. Lemmon Obs.]]
 | discovered      = 19 November 2022
 | mpc_name        = {{mp|2022 WJ|1}}
 | alt_names       = C8FF042<ref name="ProjectPluto"/><ref name="EarthSky-20221119"/>
 | pronounced      = 
 | named_after     = 
 | mp_category     = {{nowrap|[[Near-Earth object|NEO]]{{·}}[[Apollo asteroid|Apollo]]<ref name="MPC-object"/>}}
 | orbit_ref       = <ref name="jpldata" />
 | epoch           = 9 August 2022 ([[Julian day|JD]] 2459800.5)
 | uncertainty     = 6
 | observation_arc = 3.04 hours<ref name="MPC-object" />
 | earliest_precovery_date = 
 | aphelion        = 2.817 [[Astronomical unit|AU]]
 | perihelion      = 0.928 AU
 | time_periastron = May 2020 (last perihelion)<ref name="perihelion2020"/><br/>16 December 2022 (would have been)<ref name=jpldata/>
 | semimajor       = 1.872 AU
 | eccentricity    = 0.5043
 | period          = 2.56 yr (935.9 days)
 | mean_anomaly    = 310.198[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.3846605|sup=ms}} / day
 | inclination     = 2.582°
 | asc_node        = 56.748°
 | arg_peri        = 35.034°
 | moid            = {{Convert|0.000256|AU|km LD|abbr=on}}{{efn|name=MOID}}
 | jupiter_moid    = 2.418 AU
 | mean_diameter   = 0.4{{snd}}0.6 m<ref name=Kareta2024/>
 | rotation        = 
 | albedo          = 0.15{{snd}}0.35<ref name=Kareta2024/>
 | spectral_type   = 
 | magnitude       = ≈31 @ 0.2 AU<ref name="opposition2022"/><br/>≈15 (before entering [[Earth's shadow]])<ref name="MPC-object"/>
 | abs_magnitude   = {{val|33.554|0.363}}<ref name="jpldata" />
}}

'''{{mp|2022 WJ|1}}''', formerly designated '''C8FF042''', was a small, harmless ≈1-metre [[near-Earth asteroid]] or [[meteoroid]] that [[Impact event|impacted]] Earth's atmosphere on 19 November 2022 at 08:27 [[Universal Time|UT]] in [[Southern Ontario]], Canada, above the [[Golden Horseshoe]] region, southwest of [[Toronto]].<ref name="EarthSky-20221119" /><ref name=ESA-C8FF042/><ref name=Busch/> [[Meteorite]]s were detected by [[Weather radar#Meteorite fall detection|weather radar]] during [[Dark flight (astronomy)|dark flight]].

== Discovery==
The asteroid was discovered three hours before impact by David Rankin at [[Mount Lemmon Observatory]], during routine observations for the [[Mount Lemmon Survey]].<ref name="MPEC-2022-W69"/> The first image was taken at 04:53 UT when the asteroid was {{Convert|0.000859|AU|e3km e3mi LD|abbr=unit|lk=on}} from Earth.<ref name="first-image"/> Using the first four images of the asteroid, [[Sentry (monitoring system)#Scout|Scout]] estimated a 25% chance of an Earth impact.<ref name=Andrews/> The next four images raised the chance to 50%. Within about an hour, further observations raised the chance of impact to 100%. The final observation was from Mauna Kea, 32 minutes before impact, just before it entered [[Earth's shadow]].<ref name="JPL20221122"/> The asteroid brightened to about [[apparent magnitude]] 15 (about the brightness of [[Pluto]]) before disappearing into Earth's shadow.<ref name="MPC-object"/>

It is the sixth successfully-predicted asteroid impact.<ref name="ESA-C8FF042"/>{{efn|name=impactors}} With an [[absolute magnitude#Solar System bodies (H)|absolute magnitude]] of 33.6, it is the smallest asteroid discovered while it was in space.<ref name="MPC-H"/>

== Impact ==
A [[meteorite fall]] was presumed to have occurred along the south shores of [[Lake Ontario]], from east of [[Grimsby, Ontario|Grimsby]] to [[Niagara-on-the-Lake]] with most [[meteorite]]s landing in the water.<ref name="JSC-Grimsby"/> Larger fragments would have fallen farther to the east.<ref name="JSC-Grimsby"/> During [[Dark flight (astronomy)|dark flight]], [[Weather radar#Meteorite fall detection|weather radar]] signatures appeared from an altitude of ~15&nbsp;km down to 850 metres.<ref name="JSC-Grimsby"/> Meteorites should have a fresh black [[Glossary of meteoritics#F|fusion crust]].<ref name="Western20221121"/> Most findable fragments would likely be around 5 grams and the size of a [[Nickel (United States coin)|nickel]]. The [[Glossary of meteoritics#M|main mass]] might be the size of a [[Ball (association football)|soccer ball]] and be located between [[Port Weller, Ontario|Port Weller]] and Virgil.<ref name="Western20221121"/>

There was also an observed [[ordinary chondrite]] meteorite fall in Grimsby at 01:03 UT 26 September 2009 with 13 recovered meteorites totaling 215 grams (the main mass was 69 grams).<ref name="Grimsby2009"/> The 2009 fall has a [[strewn field]] of 8&nbsp;km x 4&nbsp;km.<ref name="Grimsby2009"/>

The Minor Planet Center noted that Earth's atmosphere was impacted above [[Brantford, Ontario|Brantford]] 70&nbsp;km from Grimsby.<ref name="MPEC-2022-W69"/> The resulting [[sonic boom]] was mostly heard in [[Hamilton, Ontario|Hamilton]] while the fireball was visible to observers in the [[Greater Toronto Area]] and as far as the U.S. states of [[Maryland]], [[Ohio]], [[Pennsylvania]], and [[New York (state)|New York]].<ref>{{cite news | url=https://www.nytimes.com/2022/11/19/science/fireball-asteroid-toronto-new-york.html | title=Fireball Flashes Above Ontario and Parts of the U.S. | work=The New York Times | date=19 November 2022 | last1=Holpuch | first1=Amanda }}</ref>

{| class=wikitable width=700
|[[File:2022_wj1-final-trajectory.png|400px]]<BR />Simulated final trajectory estimate from [[JPL Horizons On-Line Ephemeris System|JPL Horizons]] with 1 minute markers [[Central Time Zone|CST]] (UT-6hr) and lines down to surface.
|[[File:2022 wj1-final-trajectory2.png|300px]]<BR />View from sunlit side of Earth. Without Earth's gravity, {{mp|2022 WJ|1}}'s trajectory would have missed Earth. Red markers show inside Earth's shadow.
|}

== Orbit==
The [[Apollo asteroid]] was inbound approaching a mid-December [[perihelion]] (closest approach to the Sun) when it impacted Earth.<ref name="jpldata" /> Even at [[Opposition (astronomy)|opposition]] on 15 October 2022 when {{mp|2022 WJ|1}} was {{Convert|0.2|AU|e6km LD|abbr=unit|lk=on}} from Earth, it had an unobservable apparent magnitude of 31 which is about 600 times too faint to be detected by even the most sensitive [[Limiting magnitude#allsky|automated allsky surveys]].<ref name="opposition2022"/>{{efn|name=math}}

{{mp|2022 WJ|1}} orbited from inside Earth's orbit with perihelion at 0.92 AU to the middle of the [[asteroid belt]] at 2.8 AU.<ref name="jpldata" />

[[File:Animation of 2022 WJ1 around Sun.gif|thumb|left|280px|Animation of {{mp|2022 WJ|1}} around the Sun<br />{{legend2|Magenta|{{mp|2022 WJ|1}}}}{{·}}{{legend2| RoyalBlue| Earth}}{{·}}{{legend2|Cyan| Mars}}{{·}}{{legend2|Yellow| Sun}}]]
{{clear|left}}

== See also ==
* [[Asteroid impact prediction]]
* [[Impact event]]
* {{mpl|2022 EB|5}}, the first predicted asteroid impact in 2022

== Notes ==
{{notelist|refs=

{{efn|name=MOID|Earth [[Minimum orbit intersection distance|MOID]] as defined for 9 August 2022 roughly 100 days before Earth approach.}}

<!--
{{efn|name=size|An [[Absolute magnitude#Solar System bodies (H)|absolute magnitude]] of 33.6 and assumed [[Albedo#Astronomical albedo|albedo]] of 0.14 gives a diameter of 0.7 meters.}}
-->

{{efn|name=impactors|The other five predicted impactors are: {{mpl|2008 TC|3}}, [[2014 AA]], [[2018 LA]], [[2019 MO]], and {{mpl|2022 EB|5}}.}}

{{efn|name=math|[[Apparent magnitude#Calculations|Math]]: <math>(\sqrt[5]{100})^{31-24}\approx 630</math>}}

}} <!-- end of notelist -->

== References ==
{{reflist|refs=

<ref name="jpldata">{{cite web
  |title=JPL Small-Body Database Browser: (2022 WJ1)
  |url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2022WJ1&view=OPC
  |publisher=[[Jet Propulsion Laboratory]]
  |archive-url=https://archive.today/20221119151925/https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html%23/?sstr=2022WJ1&view=OPC
  |archive-date=2022-11-19
  |url-status=live
  |accessdate=2022-11-19}}</ref>

<ref name="MPC-object">{{cite web
  |title=2022 WJ1
  |url=https://www.minorplanetcenter.net/db_search/show_object?object_id=2022+WJ1
  |publisher=Minor Planet Center
  |accessdate=19 November 2022}}</ref>

<ref name="MPC-H">{{cite web
  |title=Minor Planets with Absolute Magnitudes 33 < H < 99
  |url=https://minorplanetcenter.net/db_search/show_by_properties?utf8=%E2%9C%93&semimajor_axis_min=&semimajor_axis_max=&eccentricity_min=&eccentricity_max=&inclination_min=&inclination_max=&argument_of_perihelion_min=&argument_of_perihelion_max=&ascending_node_min=&ascending_node_max=&mean_anomaly_min=&mean_anomaly_max=&mean_daily_motion_min=&mean_daily_motion_max=&perihelion_distance_min=&perihelion_distance_max=&aphelion_distance_min=&aphelion_distance_max=&period_min=&period_max=&absolute_magnitude_min=33&absolute_magnitude_max=99&orbit_uncertainty_min=&orbit_uncertainty_max=
  |publisher=Minor Planet Center
  |accessdate=19 November 2022}}</ref>

<ref name="MPEC-2022-W69">{{cite web
  |title=MPEC 2022-W69 : 2022 WJ1
  |url=https://minorplanetcenter.net/mpec/K22/K22W69.html
  |work=Minor Planet Electronic Circulars
  |publisher=Minor Planet Center
  |date=19 November 2022
  |accessdate=19 November 2022}}</ref>

<ref name="ProjectPluto">{{cite web
  |title="Pseudo-MPEC" for C8FF042
  |url=https://www.projectpluto.com/neocp2/mpecs/C8FF042.htm
  |publisher=Project Pluto
  |date=19 November 2022
  |url-status=live
  |archive-url=https://web.archive.org/web/20221119160540/https://www.projectpluto.com/neocp2/mpecs/C8FF042.htm
  |archive-date=19 November 2022
  |accessdate=19 November 2022}}</ref>

<ref name="EarthSky-20221119">{{cite news
  |title=Asteroid hit Canada mere hours after discovery
  |url=https://earthsky.org/space/asteroid-hit-canada-mere-hours-after-discovery/
  |first=Kelly Kizer |last=Whitt
  |work=EarthSky
  |date=19 November 2022
  |accessdate=19 November 2022}}</ref>

<ref name="perihelion2020">{{cite web
  |title=Horizons Batch for previous perihelion in May 2020
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |type=Perihelion occurs when rdot flips from negative to positive
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272022+WJ1%27&START_TIME=%272020-May-10%27&STOP_TIME=%272020-Jun-10%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2719%27
  |accessdate=2022-11-19}}</ref>

<ref name="first-image">{{cite web
  |title=Horizons Batch for Earth distance at 04:53
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272022+WJ1%27&START_TIME=%272022-11-19%2004:53%27&STOP_TIME=%272022-11-20%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2720%27
  |accessdate=2022-11-20}}</ref>

<ref name="opposition2022">{{cite web
  |title=Horizons Batch for opposition October 2022
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272022+WJ1%27&START_TIME=%272022-Oct-14%27&STOP_TIME=%272022-Oct-16%27&STEP_SIZE=%271%20day%27&QUANTITIES=%279,19,20,23%27
  |accessdate=2022-11-23}}</ref>

<ref name="JSC-Grimsby">{{cite web
  |title=Meteorite Falls: Grimsby, Ontario
  |url=https://ares.jsc.nasa.gov/meteorite-falls/events/grimsby-ontario
  |publisher=NASA [[Johnson Space Center]] Astromaterials Research & Exploration Science
  |archive-url=https://web.archive.org/web/20221120025710/https://ares.jsc.nasa.gov/meteorite-falls/events/grimsby-ontario
  |archive-date=2022-11-20
  |url-status=live
  |accessdate=2022-11-20}}</ref>

<ref name="Western20221121">{{cite web
  |title=Bright fireball may have dropped meteorites in Niagara region
  |url=https://news.westernu.ca/2022/11/niagara-meteor/
  |publisher=Western University News
  |date=2022-11-21
  |accessdate=2022-11-22}}</ref>

<ref name="JPL20221122">{{cite web
  |title=NASA Program Predicted Impact of Small Asteroid Over Ontario, Canada
  |url=https://www.jpl.nasa.gov/news/nasa-program-predicted-impact-of-small-asteroid-over-ontario-canada
  |publisher=NASA [[Jet Propulsion Laboratory|JPL]]
  |date=2022-11-22
  |accessdate=2022-11-22}}</ref>

<ref name="Grimsby2009">{{cite web
  |title=Meteoritical Society: Grimsby (2009)
  |url=https://www.lpi.usra.edu/meteor/metbull.php?code=50911
  |publisher=Meteoritical Society
  |accessdate=2022-11-22}}</ref>

<ref name=ESA-C8FF042>[https://twitter.com/esaoperations/status/1593912958509367296 ESA C8FF042 (2:23 AM 19 Nov 2022)]</ref>

<ref name=Busch>[https://twitter.com/michael_w_busch/status/1593967565818441728 Astronomer Michael Busch (6:00 AM 19 Nov 2022)]</ref>

<ref name=Andrews>[https://twitter.com/SquigglyVolcano/status/1595232452129210370 Dr Robin George Andrews (5:46 PM 22 Nov 2022)]</ref>

<ref name=Kareta2024>{{Cite journal|display-authors=etal|author=Kareta, Theodore|date=22 November 2024|title=Telescope-to-Fireball Characterization of Earth Impactor 2022 WJ<sub>1</sub>|journal=The Planetary Science Journal|volume=253|issue=5|pages=18|url=https://ui.adsabs.harvard.edu/abs/2024arXiv241114595K/abstract|doi=10.3847/PSJ/ad8b22|doi-access=free |arxiv=2411.14595}}</ref>

}}

== External links ==
* [https://fireball.amsmeteors.org/members/imo_view/event/2022/8984 Fireball observers location map]
* {{NeoDys|2022+WJ1}}
* {{ESA-SSA|2022WJ1}}
* {{JPL small body|id=54327740}}
* [https://catalina.lpl.arizona.edu/news/once-again-catalina-sky-survey-discovers-earth-impacting-asteroid Interview with the asteroid's discoverer David Rankin]

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{{DEFAULTSORT:2022 WJ1}}
[[Category:Apollo asteroids|#]]
[[Category:Astronomical objects discovered in 2022|20221119]]
[[Category:Discoveries by MLS|#]]
[[Category:Minor planet object articles (unnumbered)]]
[[Category:Predicted impact events]]
[[Category:November 2022 in Canada]]
[[Category:2022 in Ontario]]
[[Category:Modern Earth impact events]]