2022 WJ₁

2022 WJ₁
Perihelion	0.928 AU
Semi-major axis	1.872 AU
Eccentricity	0.5043
Orbital period (sidereal)	2.56 yr (935.9 days)
Mean anomaly	310.198°
Mean motion	0° 23m 4.778s / day
Inclination	2.582°
Longitude of ascending node	56.748°
Time of perihelion	May 2020 (last perihelion); 16 December 2022 (would have been)
Argument of perihelion	35.034°
Earth MOID	0.000256 AU (38,300 km; 0.100 LD)
Jupiter MOID	2.418 AU
Physical characteristics
Mean diameter	<1 m
Apparent magnitude	≈31 @ 0.2 AU; ≈15 (before entering Earth's shadow)
Absolute magnitude (H)	33.554±0.363

2022 WJ₁, formerly designated C8FF042, was a small, harmless ≈1-metre

dark flight

.

Discovery

The asteroid was discovered three hours before impact by David Rankin at

LD) from Earth.^[10] Using the first four images of the asteroid, Scout estimated a 25% chance of an Earth impact.^[11] 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.^[12] The asteroid brightened to about apparent magnitude 15 (about the brightness of Pluto) before disappearing into Earth's shadow.^[1]

It is the sixth successfully-predicted asteroid impact.[8]^[c] With an absolute magnitude of 33.6, it is the smallest asteroid discovered while it was in space.^[13]

Impact

A

Port Weller and Virgil.^[15]

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).^[16] The 2009 fall has a strewn field of 8 km x 4 km.^[16]

The Minor Planet Center noted that Earth's atmosphere was impacted above

Brantford 70 km from Grimsby.^[2] The resulting sonic boom was mostly heard in 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.^[17]

Simulated final trajectory estimate from JPL Horizons with 1 minute markers CST (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.

Orbit

The

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 sensitive automated allsky surveys.^[7]^[d]

2022 WJ₁ orbited from inside Earth's orbit with perihelion at 0.92 AU to the middle of the asteroid belt at 2.8 AU.^[5]

Notes

^ Earth MOID as defined for 9 August 2022 roughly 100 days before Earth approach.
^ An absolute magnitude of 33.6 and assumed albedo of 0.14 gives a diameter of 0.7 meters.
^ The other five predicted impactors are: 2008 TC3, 2014 AA, 2018 LA, 2019 MO, and 2022 EB5.
^ Math: $({\sqrt[{5}]{100}})^{31-24}\approx 630$

References

^ ^a ^b ^c ^d ^e "2022 WJ1". Minor Planet Center. Retrieved 19 November 2022.
^ ^a ^b ^c "MPEC 2022-W69 : 2022 WJ1". Minor Planet Electronic Circulars. Minor Planet Center. 19 November 2022. Retrieved 19 November 2022.
^ ""Pseudo-MPEC" for C8FF042". Project Pluto. 19 November 2022. Archived from the original on 19 November 2022. Retrieved 19 November 2022.
^ ^a ^b Whitt, Kelly Kizer (19 November 2022). "Asteroid hit Canada mere hours after discovery". EarthSky. Retrieved 19 November 2022.
^ ^a ^b ^c ^d ^e "JPL Small-Body Database Browser: (2022 WJ1)". Jet Propulsion Laboratory. Archived from the original on 19 November 2022. Retrieved 19 November 2022.
^ "Horizons Batch for previous perihelion in May 2020" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 19 November 2022.
^ ^a ^b "Horizons Batch for opposition October 2022". JPL Horizons. Retrieved 23 November 2022.
^ ^a ^b ESA C8FF042 (2:23 AM 19 Nov 2022)
^ Astronomer Michael Busch (6:00 AM 19 Nov 2022)
^ "Horizons Batch for Earth distance at 04:53". JPL Horizons. Retrieved 20 November 2022.
^ Dr Robin George Andrews (5:46 PM 22 Nov 2022)
^ "NASA Program Predicted Impact of Small Asteroid Over Ontario, Canada". NASA JPL. 22 November 2022. Retrieved 22 November 2022.
^ "Minor Planets with Absolute Magnitudes 33 < H < 99". Minor Planet Center. Retrieved 19 November 2022.
^ ^a ^b ^c "Meteorite Falls: Grimsby, Ontario". NASA Johnson Space Center Astromaterials Research & Exploration Science. Archived from the original on 20 November 2022. Retrieved 20 November 2022.
^ ^a ^b "Bright fireball may have dropped meteorites in Niagara region". Western University News. 21 November 2022. Retrieved 22 November 2022.
^ ^a ^b "Meteoritical Society: Grimsby (2009)". Meteoritical Society. Retrieved 22 November 2022.
^ Holpuch, Amanda (19 November 2022). "Fireball Flashes Above Ontario and Parts of the U.S." The New York Times.

External links

Fireball observers location map
2022 WJ1 at NeoDyS-2, Near Earth Objects—Dynamic Site
- Ephemerides · Observation prediction · Orbital info · MOID · Proper elements · Observational info · Close approaches · Physical info · Orbit animation
2022 WJ1 at ESA–space situational awareness
- Ephemerides · Observations · Orbit · Physical properties · Summary
2022 WJ1 at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters
Interview with the asteroid's discoverer David Rankin

[MOID-7] Earth MOID as defined for 9 August 2022 roughly 100 days before Earth approach.

[size-8] An absolute magnitude of 33.6 and assumed albedo of 0.14 gives a diameter of 0.7 meters.

[impactors-15] The other five predicted impactors are: 2008 TC3, 2014 AA, 2018 LA, 2019 MO, and 2022 EB5.

[math-21] Math: $({\sqrt[{5}]{100}})^{31-24}\approx 630$

[MPC-object-1] "2022 WJ1". Minor Planet Center. Retrieved 19 November 2022.

[MPEC-2022-W69-2] "MPEC 2022-W69 : 2022 WJ1". Minor Planet Electronic Circulars. Minor Planet Center. 19 November 2022. Retrieved 19 November 2022.

[ProjectPluto-3] ""Pseudo-MPEC" for C8FF042". Project Pluto. 19 November 2022. Archived from the original on 19 November 2022. Retrieved 19 November 2022.

[EarthSky-20221119-4] Whitt, Kelly Kizer (19 November 2022). "Asteroid hit Canada mere hours after discovery". EarthSky. Retrieved 19 November 2022.

[jpldata-5] "JPL Small-Body Database Browser: (2022 WJ1)". Jet Propulsion Laboratory. Archived from the original on 19 November 2022. Retrieved 19 November 2022.

[perihelion2020-6] "Horizons Batch for previous perihelion in May 2020" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 19 November 2022.

[opposition2022-9] "Horizons Batch for opposition October 2022". JPL Horizons. Retrieved 23 November 2022.

[ESA-C8FF042-10] ESA C8FF042 (2:23 AM 19 Nov 2022)

[Busch-11] Astronomer Michael Busch (6:00 AM 19 Nov 2022)

[first-image-12] "Horizons Batch for Earth distance at 04:53". JPL Horizons. Retrieved 20 November 2022.

[Andrews-13] Dr Robin George Andrews (5:46 PM 22 Nov 2022)

[JPL20221122-14] "NASA Program Predicted Impact of Small Asteroid Over Ontario, Canada". NASA JPL. 22 November 2022. Retrieved 22 November 2022.

[MPC-H-16] "Minor Planets with Absolute Magnitudes 33 < H < 99". Minor Planet Center. Retrieved 19 November 2022.

[JSC-Grimsby-17] "Meteorite Falls: Grimsby, Ontario". NASA Johnson Space Center Astromaterials Research & Exploration Science. Archived from the original on 20 November 2022. Retrieved 20 November 2022.

[Western20221121-18] "Bright fireball may have dropped meteorites in Niagara region". Western University News. 21 November 2022. Retrieved 22 November 2022.

[Grimsby2009-19] "Meteoritical Society: Grimsby (2009)". Meteoritical Society. Retrieved 22 November 2022.

[20] Holpuch, Amanda (19 November 2022). "Fireball Flashes Above Ontario and Parts of the U.S." The New York Times.

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