Asteroid 2015 ET passed by the Earth at a distance of 125 000 km (0.33 times the average distance between the Earth and the Moon, or 0.08% of the average distance between the Earth and the Sun), slightly after 4.40 pm GMT on Tuesday 10 March 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 ET has an estimated equivalent diameter of 8-27 m (i.e. it is estimated that a spherical object with the same volume would be 8-27 m in diameter), and an object of this size would be expected to break up in the atmosphere between 35 and 18 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2015 ET. JPL Small Body Database.
2015 ET was discovered on 11 March 2015 (the day after its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2015 ET implies that it was the 19th asteroid (asteroid T) discovered in the first half of March 2015 (period 2015 E).
2015 ET has an 1078 day orbital period and an eccentric orbit tilted at an angle of 0.24° to the plane of the Solar System, which takes it from 0.86 AU from the Sun (i.e. 86% of the average distance at which the Earth orbits the Sun) to 3.25 AU from the Sun (i.e. 325% of the average distance at which the Earth orbits the Sun, greater than twice the distance at which the planet Mars orbits the Sun). 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 2012 and the next predicted in November 2017 this year. 2015 ET also occasionally makes close passes of the planet Venus, with the next such encounter predicted in June 2032.
See also...
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Asteroid 2015 DS passes the Earth.Asteroid 2015 DS passed by the Earth at a distance of 6 590 000 km (17.1 times the average distance between the Earth and the Moon, or 4.40% of the average distance between the Earth and the Sun), slightly before 10.55 am GMT on Monday 9 March 2015. There was...
Asteroid 2015 DK200 passes the Earth.
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