Asteroid (445830) 2012 CL19 passed by the Earth at a distance of 6 687 000 km (17.4 times the average distance between the Earth and the Moon, or 4.47% of the average distance between the Earth and the Sun), slightly after 11.15 pm GMT on Saturday 3 October 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented a considerable threat. (445830) 2012 CL19 has an estimated equivalent diameter of 71-230 m (i.e. a spherical body with the same mass would be 71-230 m in diameter), and an object towards the upper end of this range would pass through the atmosphere and directly impact the ground with a force of about 350 megatons (about 20 600 times the explosive energy of the Hiroshima bomb), causing devastation over a wide area and creating a crater over 3 km across, and resulting in global climatic problems that could last for years or even decades.
The calculated orbit of 2015 RM83. JPL Small Body Database.
(445830) 2012 CL19 was discovered on 11 February 2012 by the University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount Lemmon in the Catalina Mountains north of Tucson. The designation 2012 CL19 implies that the asteroid was the 486th object (object L19) discovered in the first half of February 2012 (period 2012 C), while the designation 445830 implies that it was 445 830th asteroid ever discovered (asteroids are not given this longer designation immediately to avoid naming double or false sightings).
(445830) 2012 CL19 has a 713 day orbital period and an eccentric orbit that takes it from 0.87 AU from the Sun (i.e. 87% of the average distance at which the Earth orbits the Sun) to 2.25 AU from the Sun (i.e. 225% of the average distance at which the Earth orbits the Sun, considerably outside orbit of the planet Mars). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). As an asteroid possibly larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (445830) 2012 CL19 is also classified as a Potentially Hazardous Asteroid. (445830) 2012 CL19 also has occasional close encounters with the planet Mars, the last having occurred in January 1996 and the next predicted for February 2063.
See also...
Asteroid 2015 RM83 passed by the Earth at a distance of 15 580 000 km (40.5 times the average distance between the Earth and the Moon, or 10.4% of the average distance between the Earth and the Sun), slightly before 6.20 am GMT on Saturday 12...
Asteroid 2015 OV passed by the Earth at a distance of 11 220 000 km (29.2 times the average distance between the Earth and the Moon, or 7.50% of the average distance between the Earth and the Sun), slightly after midday GMT on Monday 24 August...
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