Asteroid (494999) 2010 JU39 passed by the Earth at a distance of about 9 006 000
km (23.5 times the average distance between the Earth and the Moon, or 6.02% of the distance between the Earth and the Sun), slightly after 3.40 pm
GMT on Friday 28 June 2019. There was no danger of
the asteroid hitting us, though were it to do so it would have
presented a significant threat. (494999) 2010 JU39 has an estimated
equivalent
diameter of 230-720 m (i.e. it is estimated that a spherical object
with
the same volume would be 230-720 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 between about 17 500 and 1 100 000 times as
powerful
as the
Hiroshima
bomb. Such an impact would result in an impact crater between 3 and 11 km
in
diameter
and devastation on a global scale, as well as climatic effects that
would last decades or even centuries.
The calculated orbit of (494999) 2010 JU39. JPL Small Body Database.
(494999) 2010 JU39 was discovered on 9 May 2010 by the
University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount
Lemmon in the Catalina Mountains north of Tucson. The designation 2010 JU39
implies that the asteroid was the 956th object (asteroid U39 -
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 U39 = 20 + (24 X 39) = 956) discovered in the first half of May 2010 (period 2010 J).
(494999) 2010 JU39 has a 322 day orbital period, with an elliptical orbit tilted at
an angle of 36.2° to the plain of the Solar System which takes in to
0.42 AU from the Sun (42% of the distance at which the Earth orbits the
Sun, and slightly more than the distance at which Merculry orbits the Sun) and out to
1.42 AU (42%
further away from the Sun than the Earth, and slightly inside the orbit of the planet Mars). This means that close
encounters between the asteroid and Earth are fairly common, with the
last thought to have happened in February 2017 and the next predicted
in January 2025. Although it does cross the Earth's
orbit and is briefly
further from the Sun on each cycle, (494999) 2010 JU39 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, (494999) 2010 JU39 is also
classified as a Potentially Hazardous Asteroid.
See also...
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