Asteroid 2019 OT passed by the Earth at a distance of about 6 627 000 km (17.3 times the average distance between the Earth and the Moon, or 4.43% of the distance between the Earth and the Sun), slightly after 9.25 am GMT on Tuesday 23 July 2019. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2019 OT has an estimated equivalent diameter of 140-460 m (i.e. it is estimated that a spherical object with the same volume would be 140-460 m in diameter), and an object of this size would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be between about 7500 and 300 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater between 2 and 8 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.
2019 OT was discovered on 24 July 2019 (the day after its closest approach to the Earth) by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2019 OT implies that the asteroid was the 19th object (object T - in numbering asteroids the letters A-Z, excluding I, are assigned numbers from 1 to 25, so that T = 19) discovered in the second half of July 2019 (period 2019 O).
2019 OT has an 820 day orbital period and an eccentric orbit tilted at an angle of 47.3° to the plane of the Solar System, which takes it from 0.77 AU from the Sun (i.e. 77% of he average distance at which the Earth orbits the Sun) to 2.66 AU from the Sun (i.e. 2.66% of the average distance at which the Earth orbits the Sun, which is almost twice the distance at which the planet Mars orbits). 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 probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2019 OT is also classified as a Potentially Hazardous Asteroid.
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