 Orbit before impact | |
| Discovery[1][2] | |
|---|---|
| Discovered by | David Rankin (Mt. Lemmon Srvy) |
| Discovery site | Mt. Lemmon Obs. |
| Discovery date | 19 November 2022 |
| Designations | |
| 2022 WJ1 | |
| C8FF042[3][4] | |
| NEO · Apollo[1] | |
| Orbital characteristics[5] | |
| Epoch 9 August 2022 (JD 2459800.5) | |
| Uncertainty parameter 6 | |
| Observation arc | 3.04 hours[1] |
| Aphelion | 2.817AU |
| Perihelion | 0.928 AU |
| 1.872 AU | |
| Eccentricity | 0.5043 |
| 2.56 yr (935.9 days) | |
| 310.198° | |
| 0° 23m 4.778s / day | |
| Inclination | 2.582° |
| 56.748° | |
| May 2020 (last perihelion)[6] 16 December 2022 (would have been)[5] | |
| 35.034° | |
| Earth MOID | 0.000256 AU (38,300 km; 0.100 LD)[a] |
| Jupiter MOID | 2.418 AU |
| Physical characteristics | |
| 0.4 – 0.6 m[7] | |
| 0.15 – 0.35[7] | |
| ≈31 @ 0.2 AU[8] ≈15 (before enteringEarth's shadow)[1] | |
| 33.554±0.363[5] | |
2022 WJ1, formerly designatedC8FF042, was a small, harmless ≈1-metrenear-Earth asteroid ormeteoroid thatimpacted Earth's atmosphere on 19 November 2022 at 08:27UT inSouthern Ontario, Canada, above theGolden Horseshoe region, southwest ofToronto.[4][9][10] A fireball was widely visible.Meteorites were also detected byweather radar duringdark flight.
It was the 6th asteroid in history to be discovered before impact.
The asteroid was discovered three hours before impact by David Rankin atMount Lemmon Observatory, during routine observations for theMount Lemmon Survey.[2] The first image was taken at 04:53 UT when the asteroid was 0.000859 AU (128.5 thousand km; 79.8 thousand mi; 0.334 LD) from Earth.[11] Using the first four images of the asteroid,Scout estimated a 25% chance of an Earth impact.[12] 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 enteredEarth's shadow.[13] The asteroid brightened to aboutapparent magnitude 15 (about the brightness ofPluto) before disappearing into Earth's shadow.[1]
It is the sixth successfully-predicted asteroid impact.[9][b] With anabsolute magnitude of 33.6, it is the smallest asteroid discovered while it was in space.[14]
Ameteorite fall was presumed to have occurred along the south shores ofLake Ontario, from east ofGrimsby toNiagara-on-the-Lake with mostmeteorites landing in the water.[15] Larger fragments would have fallen farther to the east.[15] Duringdark flight,weather radar signatures appeared from an altitude of ~15 km down to 850 metres.[15] Meteorites should have a fresh blackfusion crust.[16] Most findable fragments would likely be around 5 grams and the size of anickel. Themain mass might be the size of asoccer ball and be located betweenPort Weller and Virgil.[16]
There was also an observedordinary 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).[17] The 2009 fall has astrewn field of 8 km x 4 km.[17]
The Minor Planet Center noted that Earth's atmosphere was impacted aboveBrantford 70 km from Grimsby.[2] The resultingsonic boom was mostly heard inHamilton while the fireball was visible to observers in theGreater Toronto Area and as far as the U.S. states ofMaryland,Ohio,Pennsylvania, andNew York.[18]
 Simulated final trajectory estimate fromJPL Horizons with 1 minute markersCST (UT-6hr) and lines down to surface. |  View from sunlit side of Earth. Without Earth's gravity,2022 WJ1's trajectory would have missed Earth. Red markers show inside Earth's shadow. |
TheApollo asteroid was inbound approaching a mid-Decemberperihelion (closest approach to the Sun) when it impacted Earth.[5] Even atopposition on 15 October 2022 when2022 WJ1 was 0.2 AU (30 million km; 78 LD) from Earth, it had an unobservable apparent magnitude of 31 which is about 600 times too faint to be detected by even the most sensitiveautomated allsky surveys.[8][c]
2022 WJ1 orbited from inside Earth's orbit with perihelion at 0.92 AU to the middle of theasteroid belt at 2.8 AU.[5]
2022 in space | ||
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Space probe launches |
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| Impact events | ||
| SelectedNEOs | ||
| Discoveries | ||
| Comets | ||
| Space exploration | ||
