Slightly before 9.20 pm local time (8.20 pm GMT) on Sunday 12 February 2023, Hungarian astronomer Krisztián Sárneczky of the Konkoly Observatory observed a Near Earth Object moving rapidly across the northern sky. He recorded this as SAR2667, and reported the finding to the International Astronomical Union's Minor Planet Centre, where the sighting was confirmed, and given the provisional designation 2023 CX1, which implies that it was the 48th asteroid (object X1 - in numbering asteroids the letters A-Z, excluding I, are assigned numbers from 1 to 25, with a number added to the end each time the alphabet is ended so that A = 1, A1 = 26, A2 = 51, etc., which means that X1 = 25 + 23 = 48) discovered in the first half of February 2023 (period 2023 C - the year being split into 24 half-months represented by the letters A-Y, with I being excluded). Later that evening the European Space Agency announced that it's scientists had calculated the asteroid was likely to impact the Earth the following day, somewhere around the French city of Rouen.
Slightly before 3.00 am GMT on Monday 13 February, witnesses across southern England and Wales, northern France, most of Belgium, the southern part of the Netherlands and western Germany reported seeing a bright fireball over the English Channel, disappearing somewhere to the north of Dieppe. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry, although on this occasion the object was confirmed to be the newly discovered asteroid, 2023 CX1.
Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).
These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.
Asteroid 2023 CX1 is calculated to have been about 233 000 km from the Earth (i.e. about 61% of the distance to the Moon) when it was discovered, and to previously have had a 799 day (2.19 year) orbital period, with an elliptical orbit tilted at an angle of 3.56° to the plain of the Solar System which took in to 0.92 AU from the Sun (92% of the distance at which the Earth orbits the Sun) and out to 2.45 AU (245% of the distance at which the Earth orbits the Sun, and more than the distance at which the planet Mars orbits the Sun). It would therefore have been 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 Asteroid 2023 CX1 had occasional close encounters with the Earth, with the last having happened in June 2000.
Asteroid 2023 CX1 is thought to have had a diameter of about a metre, and to have exploded in an airburst 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) more than 40 km above the English Channel. Nevertheless, it was calculated that the asteroid could potentially have scattered fragments on the coast of Normandy between Dieppe and Doudeville, with the potential to have produced pieces as large as 2 kg. A search was organised by the Fireball Recovery and Interplanetary Observation Network involving many volunteers and researchers, who assembled on Wednesday 15 February to scour this area. This led to the discovery of a single fragment in a field close to the town of Saint-Pierre-le-Viger, by student Loïs Leblanc.
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