Asteroid
(457662) 2009 DZ passed by the Earth at a distance of 12 510 000 km
(32.5 times the average distance between the Earth and the Moon, or 8.36% of the average distance between the Earth and the Sun), slightly before 2.35 am GMT on Tuesday 23 February 2016. There was no danger of
the asteroid hitting us, though had it done so it would have presented a
considerable threat.
(457662) 2009 DZ has an estimated equivalent
diameter of 75-250 m (i.e. a spherical body with the same mass would be
75-250 m in diameter), and an object towards the upper end of this range
would pass through the atmosphere and directly impact the ground with a
force of about 600 megatons (about 35 000 times the
explosive energy of
the Hiroshima bomb), causing devastation over a wide area and creating a
crater about 4 km across, and resulting in global climatic problems that
could last for decades.
(457662) 2009 DZ was discovered on 18 February 2009 by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research Laboratory in Socorro, New Mexico.
The designation 2009 DZ implies that it was the 25th asteroid
(asteroid Z) discovered in the second half of February 2009 (period 2009 Z). The
longer designation, (457662), indicates that the asteroid was the 457 662nd asteroid ever discovered. Asteroids are not given this longer
designation immediately, to avoid duplicate or false sightings.
(457662) 2009 DZ has a 639 day year orbital period and an eccentric orbit tilted at an angle of 14.1° to the plane of the Solar System that takes it from 1.01 AU from the Sun (i.e. 101 % of the average distance at which the Earth orbits the Sun) to 1.89 AU from the Sun (i.e. 189% of the average distance at which the Earth orbits the Sun, considerably outside the orbit of the planet Mars). It is therefore classed as an Amor Group Asteroid (an asteroid which comes close to the Earth, but which is always outside the Earth's orbit). This means that close encounters between the asteroid and Earth are fairly common, with the most recent having occurred in February 2009 next predicted in February 2023 . As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (457662) 2009 DZ is also classified as a Potentially Hazardous Asteroid (it comes no closer to the Sun than 101% of the average distance at which the Earth orbit's the Sun, but the Earth's orbit is not completely circular).
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