Witnesses across the Netherlands, Belgium, England, and northern France, have reported observing a bright fireball slightly after 6.50 am local time GMT on Friday 22 January 2021. The fireball is described as having moved from north to south, appearing over the Schelde Estuary and passing between the cities of Antwerp and Gent. 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.
The 22 January 2021 fireball meteor seen from Almere in the Netherlands. Timo De Frys/American Meteor Society.
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).
Heat map of northwest Europe
showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the
apparent path of the object (blue arrow). American Meteor Society.
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.
The meteor was first detected at an altitude of about 70 km and disappeared at an altitude of about 27 km, which would indicate an initial object with an approximate equivalent
diameter of 25 m (i.e. it can be estimated that a spherical object
with
the same volume would be 25 m in diameter), and had an initial velocity of about 16 km per second, decelerating to about 8 km per second before disappearing, according to the Fireball Recovery and InterPlanetary Observation Network. This makes it highly likely that fragments of the object may have reached the ground.
The trajectory of the 22 January 2021 meteor above Belgium. FRIPON/Meteor News.
Based upon this information, Simon Jean of the Observatoire de Paris has estimate that the object would have had an original orbit tilted at an angle of 20.1° to the plain of the Solar System, which took it from 0.96 AU from the Sun (96% of the distance at which the Earth orbits the
Sun) and a semi-major axis (average distance form the Sun of 1.28 (128% of the distance at which the Earth orbits
the Sun). Such an object would 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).
See also...
