Asteroid 2015 DP155 passed by the Earth at a distance of about 3 455 200 km (8.96 times the average distance between the Earth and the Moon, or 2.30% of the distance between the Earth and the Sun), slightly after 5.50 am GMT on Monday 11 June 2018. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2015 DP155 has an estimated equivalent diameter of 94-300 m (i.e. it is estimated that a spherical object with the same volume would be 90-300 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 65 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater over 4.5 km in diameter and devastation on a global scale, as well as climatic effects that would last years or even decades.
2015 DP155 was discovered on 17 February 2015 by the University of Hawaii's PANSTARRS telescope. The designation 2015 DP155 implies that the asteroid was the 3890th object (object P155) discovered in the second half of February 2015 (period 2015 D).
2015 DP155 has a 552 day orbital period and an eccentric orbit tilted at an angle of 5.38° to the plane of the Solar System, which takes it from 1.02 AU from the Sun (i.e. 102% of he average distance at which the Earth orbits the Sun) to 1.60 AU from the Sun (i.e. 160% 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 April 2015 and the next predicted in June 2021. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2015 DP155 is also classified as a Potentially Hazardous Asteroid. 2015 DP155 also has occasional close encounters with the planet Mars, with the last having occurred in March 2004, and the next predicted for April 2026.
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