Asteroid 2020 DM4 passed by the Earth at a distance of about 7 063 000 km (18.4 times the average distance between the Earth and the Moon, or 4.72% of the distance between the Earth and the Sun), at about 10.05 am GMT on Friday 1 May 2020. There was no danger of the asteroid hitting us, though were it to do so it would have presented a considerable threat. 2020 DM4 has an estimated equivalent diameter of 84-260 m (i.e. it is estimated that a spherical object with the same volume would be 84-260 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 35 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater almost 4 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.
2020 DM4 was discovered on 26 February 2020 (over two months before its closest encounter with the Earth) by the Purple Mountain Observatory of the Chinese Academy of Sciences. The designation 2020 DM4 implies that it was the 108th asteroid (asteroid X4 - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 24, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 25, A2 = 49, etc., which means that M4 = 12 + (24 X 4) = 108) discovered in the second half of February 2020 (period 2020 D).
2020 DM4 has a 947 day (2.59 year) orbital period, with an elliptical orbit tilted at an angle of 4.12° to the plain of the Solar System which takes in to 1.02 AU from the Sun (102% of the distance at which the Earth orbits the Sun) and out to 2.75 AU (275% of the distance at which the Earth orbits the sun and further from the Sun than the planet Mars). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in June 2007 and the next predicted in April 2033. It is therefore classed as an Amor Group Asteroid (an asteroid which comes close to the Earth, but which is never closer to the Sun than the Earth is). As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2020 DM4 is also classified as a Potentially Hazardous Asteroid. 2020 DM4 also has occassional close encounters with the planet Mars, with the last having happened in June 2004, and the next predicted for January 2075.
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