A fiery ball in the sky: the smallest known asteroid has fallen to Earth (photo).

A recent study revealed that in November 2022, the smallest asteroid ever detected and measured fell to Earth before exploding in the atmosphere over Canada. This asteroid, which was spotted just a few hours prior to its atmospheric entry, was about the size of an average cat. The research was published in The Planetary Science Journal, according to Live Science.

On November 19, 2022, an asteroid named 2022 WJ1 entered Earth's atmosphere, having been first identified by astronomers only a few hours before its impact. Due to intense friction with the air, the asteroid broke apart, but not before illuminating the sky over Niagara Falls with a brilliant green light. The falling rock appeared as a green fireball, leaving a bright trail in the sky during its flight. When the asteroid disintegrated, a loud explosion was heard, lasting just 10 seconds. Residents in various regions of Canada and the U.S. witnessed this event.

The authors of the new study determined that 2022 WJ1 is the smallest asteroid that has ever fallen to Earth and has been accurately measured among all known asteroids.

Astronomers detected the asteroid only 3 hours before its arrival and closely monitored its flight trajectory. Scientists analyzed the data collected at that time and concluded that the asteroid measured between 40 to 60 cm. Although small asteroids frequently fall to Earth, none have been accurately measured because astronomers notice their approach too late.

The detection of asteroid 2022 WJ1 before it struck Earth's atmosphere was only the sixth such instance where astronomers managed to observe a space rock a few hours prior to its arrival. However, until then, precise measurements of similar asteroids had not been conducted, as they are mostly seen only when they explode into a fireball.

Scientists were able to determine the size of the falling rock by observing its flight trajectory in space, its brightness, and comparing this data with observations of the fireball in the atmosphere. To date, astronomers have successfully detected an asteroid before it fell to Earth 10 times, with three of these instances occurring in 2024.

According to researchers, more data about space rocks that have fallen to Earth can be gathered from fragments that reached the surface as meteorites. However, no fragments of 2022 WJ1 have been found yet. Scientists believe that most of its debris fell into Lake Ontario after the explosion, but this does not mean that parts of the asteroid’s meteorites cannot be found on land. The study authors express hope of discovering them.