Asteroid 2017 NS5 passes the Earth.

Asteroid 2017 NS5 passed by the Earth at a distance of about 5 136 000 km (13.4 times the average distance between the Earth and the Moon, or 3.43% of the distance between the Earth and the Sun), at about 8.10 am GMT on Monday 17 July 2017. There was no danger of the asteroid hitting us, though were it to do so it would have presented a considerable threat. 2017 NS5 has an estimated equivalent diameter of 138-410 m (i.e. it is estimated that a spherical object with the same volume would be 138-410 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 3000-165 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 2-7 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.

 Image of 2017 NS5 taken with the iTelescope T17 Deep Field Research Telescope at Siding Spring Observatory in New South Wales on 11 July 2017. The image is a composite of six fifty second exposures, the dotted lines being stars which have moved over the course of the exposures and the asteroid the faint object inset indicated by the arrow. Marian Urbanik/iTelescope/Fotografický občasník.

2017 NS5 was discovered on 10 July 2017 (seven days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2017 NS5 implies that it was the 143rd asteroid (asteroid S5) discovered in the first half of July 2017 (period 2017 N).

The calculated orbit of 2017 NS1. Minor Planet Center.

2017 NS1 has a 353 day orbital period, with an elliptical orbit tilted at an angle of 44.0° to the plain of the Solar System which takes in to 0.72 AU from the Sun (72% of the distance at which the Earth orbits the Sun; slightly inside the orbit of the planet Venus) and out to 1.23 AU (23% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in July 2016 and the next predicted in July 2018. 2017 NS1 also has occasional close encounters with the planet Venus, with the next predicted for February 2148. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2017 NS1 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2017 NS1 is also classified as a Potentially Hazardous Asteroid.

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