Asteroid 2018 DU passed by the Earth at a distance of about 284 000 km (0.74 times the average distance between the Earth and the Moon, or 0.19% of the distance between the Earth and the Sun), slightly after 6.20 pm GMT on Sunday 25 February 2018. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2018 DU has an estimated equivalent diameter of 4-13 m (i.e. it is estimated that a spherical object with the same volume would be 4-13 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 43 and 27 km above the ground, with only fragmentary material reaching the Earth's surface.
120 second image of 2018 DU taken with the TENEGRA III Telescope at he Tenegra Observatory in Arizona on 25 February 2018. The longer lines are stars, their elongation being caused by the telescope tracking the asteroid over the length of the exposure. Gianluca Masi/Virtual Telescope/Michael Swartze/Tenegra Observatory.
2018 DU was discovered on 23 February 2018 (two days before its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2018 DU implies that it was the 20th asteroid (asteroid U) discovered in the second half of February 2018 (period 2018 D).
2018 DU has a 465 day orbital period and an eccentric orbit tilted at an angle of 3.20° to the plane of the Solar System, which takes it from 0.96 AU from the Sun (i.e. 96% of he average distance at which the Earth orbits the Sun) to 1.38 AU from the Sun (i.e. 138% 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 2018 DU has occasional close encounters with the Earth, with the last having happened in June 2014 and the next predicted for June this year. The asteroid also has occasional close encounters with the planet Mars, with the next predicted for October this year.
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