Asteroid 2017 WY14 passed by the Earth at a distance of about 8 792 000 km (23.2 times the average distance between the Earth and the Moon, or 5.88% of the distance between the Earth and the Sun), slightly after 7.45 am GMT on Sunday 6 May 2018. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2017 WY14 has an estimated equivalent diameter of 75-240 m (i.e. it is estimated that a spherical object with the same volume would be 75-240 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 30 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater over 2.5 km in diameter and devastation on a global scale, as well as climatic effects that would last years or even decades.
2017 WY14 was discovered on 22 November 2017 by the University of Hawaii's PANSTARRS telescope. The designation 2017 WY14 implies that the asteroid was the 724th object (object Y14) discovered in the second half of November 2017 (period 2017 W).
2017 WY14 has a 542 day orbital period and an eccentric orbit tilted at an angle of 27.7° to the plane of the Solar System, which takes it from 0.90 AU from the Sun (i.e. 90% of he average distance at which the Earth orbits the Sun) to 1.70 AU from the Sun (i.e. 170% of the average distance at which the Earth orbits the Sun, and further 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). 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 November 2020. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2006 UF17 is also classified as a Potentially Hazardous Asteroid. 2017 WY14 also has occasional close encounters with the planet Mars, with the last having occurred in May 2013.
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