2019 orbits near the ecliptic plane out to the asteroid belt and inside the orbit of Venus
|Discovered by||SONEAR Obs.|
|Discovery site||SONEAR Obs. (Y00)|
|MPC designation||2019 OK|
|Apollo · NEO|
|Orbital characteristics |
|Epoch 27 April 2019 (JD 2458600.5)|
|Uncertainty parameter 1|
|Observation arc||2.42 years|
|Earliest precovery date||2017-02-21 (Pan-STARRS)|
|2.72 yr (993 d)|
|0° 21m 45.36s / day|
|Earth MOID||0.00036 AU (54,000 km) (0.14 LD)|
|57–130 m (187–426 ft)|
2019 OK[a] is a near-Earth asteroid noted for its sudden, surprise discovery on the day before its close flyby in 2019. The object's size is estimated at 57 to 130 metres (187 to 426 ft) across, the closest asteroid of such size discovered in 2019. It is uncommon for asteroids of this size to pass within 100,000 km of Earth.
The first valid detection occurred on 24 July 2019, when it was 0.01 AU (1,500,000 km; 930,000 mi) from Earth and had an apparent magnitude of 14.7. The full moon on 16 July 2019 slowed down the discovery rate during mid-July. The asteroid was detected by Cristóvão Jacques, Eduardo Pimentel and João Ribeiro at the SONEAR Observatory 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 earlier 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 constellation Capricornus and the bright moon. The Pan-STARRS1 telescope recorded an image of 2019 OK on 28 June 2019 when it was 0.39 AU (58,000,000 km; 36,000,000 mi) 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, because it was moving directly towards the observer, its apparent motion was extremely slow, with a rate of 0.01 degrees/day, and it was not recognized as a moving object.
Orbit and classification
The asteroid is a member of the Flora family (402), a giant 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.
On 25 July 2019 at 01:22 UTC it had its closest approach to Earth, when it passed about 0.00047697 AU (71,354 km; 44,337 mi)—less than one-fifth of the distance to the Moon. Its speed was nearly 88,500 kilometres (55,000 mi) per hour.
On 28 July 2116 the asteroid will pass about 0.03 AU (4,500,000 km; 2,800,000 mi) from Earth.
Close flybys of larger asteroids
|(308635) 2005 YU55||2011-11-08||324||21.9||140|
Asteroids in the 20-meter Chelyabinsk meteor size range to 50-meter 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 17 meters to 94 meters depends on the objects albedo (how reflective it is).
Potential impact effects
If 2019 OK had been around 100+ meters in diameter an Earth impact could have released as much power as the 50 megatons generated by Tsar Bomba. If 2019 OK had been around the middle of the size estimates it could 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 had been on the smaller size it still could have released over 30 times the energy of the atomic blast by Little Boy at Hiroshima.
- "2019 OK". Minor Planet Center. Retrieved 28 July 2019.
- Gray, Bill. "Pseudo-MPEC for 2019 OK = S511618 = asassn3". Project Pluto. Retrieved 1 August 2019.
- "JPL Small-Body Database Browser: (2019 OK)" (2019-07-25 last obs.). Jet Propulsion Laboratory. Retrieved 28 July 2019.
- Mannix, Liam. "Earth had a near-miss with a 'city-killer' asteroid". stuff.co.nz. Retrieved 26 July 2019.
- "MPEC 2019-O56 : 2019 OK". IAU Minor Planet Center. 25 June 2019. Retrieved 31 July 2019. (K19O00K)
- Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). "Identification and Dynamical Properties of Asteroid Families" (PDF). Asteroids IV: 297–321. arXiv:1502.01628. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. Retrieved 28 July 2019.
- Haynes, Korey. "A large asteroid just zipped between Earth and the Moon". astronomy.com. Retrieved 26 July 2019.
- Chiu, Allyson (26 July 2019). "'It snuck up on us': Scientists stunned by 'city-killer' asteroid that just missed Earth". The Washington Post. Retrieved 27 July 2019.
- Asteroid Size Estimator using H=26 albedo=0.25 and H=24 albedo=0.05
- Asteroid Danger Explained (ESA)
- The day Earth had a near-miss with a 'city-killer' asteroid. Liam Mannix, The Sydney Herald 25 July 2019.
- 2019 OK at NeoDyS-2, Near Earth Objects—Dynamic Site
- 2019 OK at the IAU Minor Planet Center
- 2019 OK at the JPL Small-Body Database