Asteroid 2019 RB2 passed by the Earth at a distance of about 424 700
km (1.11 times the average distance between the Earth and the Moon, or
0.28% of the distance between the Earth and the Sun), slightly before 6.14 am
GMT on Wednesday 4 September 2019. There was no danger of
the asteroid hitting us, though were it to do so it would not have
presented a significant threat. 2019 RB2 has an estimated
equivalent
diameter of 5-17 m (i.e. it is estimated that a spherical object
with
the same volume would be 5-17 m in diameter), and an object of this
size
would be expected to explode in
an airburst (an explosion caused by superheating from friction with the
Earth's atmosphere, which is greater than that caused by simply
falling, due to the orbital momentum of the asteroid) in the atmosphere between 40 and 25 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2019 RB2. JPL Small Body Database.
2019 RB2 was discovered on 5 September 2019 (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 2019 RB2 implies that it was the 50th asteroid (asteroid B2 -
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 B2 = 2 + (24 X 2) = 50)
discovered in the first half of September 2019 (period 2019 R).
2019 RB2 is
calculated to have
an 904 day orbital period and an eccentric orbit
tilted at an angle of 2.70° to the plane of the Solar System, which
takes it from 1.00 AU from the Sun (i.e. the the average distance
at
which the Earth orbits the Sun) to 2.65 AU from the Sun (i.e. 265% of
the
average distance at which the Earth orbits the Sun, outside the orbit of 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 the Earth are quite common, with the
next predicted
for June 2024.
