Asteroid 2018 NU passed by the Earth at a distance of about 928 600 km (2.24 times the average distance between the Earth and the Moon, or 0.62% of the distance between the Earth and the Sun), at about 6.40 pm GMT on Friday 6 July 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 NU has an estimated equivalent diameter of 14-43 m (i.e. it is estimated that a spherical object with the same volume would be 14-43 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 28 and 10 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2018 NU. Minor Planet Center.
2018 NU was discovered on 7 July 2018 (the day after its closest approach to the Earth) by the Palomar Transient Factory at Palomar Observatory. The designation 2018 NU implies that it was the 20th asteroid (asteroid U) discovered in the first half of July 2018 (period 2018 N).
2018 NU has a 835 day orbital period and an eccentric orbit tilted at an angle of 13.1° 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 247 AU from the Sun (i.e. 247% of the average distance at which the Earth orbits the Sun, and more distant from the Sun than 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).
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