Asteroid 2004 LB passed by the Earth at a distance of about 18 954 000 km (48.3 times the average distance between the Earth and the Moon, or 12.7% of the distance between the Earth and the Sun), slightly after 2.00 pm GMT on Wednesday 6 June 2018. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2004 LB has an estimated equivalent diameter of 90-280 m (i.e. it is estimated that a spherical object with the same volume would be 90-280 m in diameter), and an object at the upper end of this range 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 about 60 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater about 4.5 km in diameter and devastation on a global scale, as well as climatic effects that would last years or even decades.
2004 LB was discovered on 7 June 2004 by the Lowell Observatory Near-Earth-Object Search, at Anderson Mesa Station, near Flagstaff, Arizona. The designation 2004 LB implies that it was the second asteroid (asteroid B) discovered in the first half of June 2004 (period 2004 L),
2004 LB has an 394 day orbital period and an eccentric orbit tilted at an angle of 37.3° to the plane of the Solar System, which takes it from 1.00 AU from the Sun (i.e. the average distance at which the Earth orbits the Sun) to 1.11 AU from the Sun (i.e. 111% of the average distance at which the Earth orbits the Sun). 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). This means that close encounters between the asteroid and Earth are extremely common, with the last having occurred in November 2017 and the next predicted in December 2018. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2004 LB is also classified as a Potentially Hazardous Asteroid.
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