A significant object has just passed through our planet's vicinity without incident. This passage, although safe, has captured the full attention of astronomers worldwide.
This is asteroid 2025 FA22, first spotted last March. Its trajectory sparked keen interest because initial estimates suggested a tiny possibility of collision with Earth by 2089. However, additional observations have dispelled these concerns. This rocky body, comparable in size to a skyscraper, passed us at a distance of 519,000 miles (835,000 km) on September 18, a little more than twice the Earth-Moon distance.
A celestial object under close surveillance
Scientists carefully monitor so-called near-Earth asteroids, which are capable of crossing Earth's orbit. Those larger than 460 feet (140 meters) are considered priorities, as their impact consequences would be major.
2025 FA22 measures between 430 and 950 feet (130 and 290 meters) in diameter, a size sufficient to level an entire metropolis. It has therefore logically been among the most scrutinized objects by the European Space Agency. Its collision probability, initially estimated at 0.01%, was reassessed to zero after an intensive observation campaign.
The Torino Scale serves as a reference for assessing risk levels, graded from 0 to 10. Upon its discovery, the asteroid reached level 1, before being downgraded to level 0 after analysis.
A scientific and technical opportunity
The September 18 passage represented a rare opportunity for data collection. The asteroid moved at nearly 24,000 mph (38,600 km/h), reaching a brightness that made it accessible to some amateur telescopes.
Radar observations conducted by NASA's Goldstone facility aim to refine the object's size and morphology. This information is essential for understanding its composition and behavior in case of interaction with a deflection device.
This approach also served as a full-scale exercise for the International Asteroid Warning Network (IAWN). The goal is to simulate an impact scenario and coordinate exchanges between institutions to improve emergency protocols.
Astronomers emphasize that 2025 FA22 is not done with our planet. Several close approaches are expected in the coming centuries, offering as many opportunities to refine observations and defense methods for future generations of astronomers.
A global training campaign
IAWN has chosen 2025 FA22 as the central subject of an observation campaign extending until the end of October. Working groups focus particularly on astrometry and polarimetry.
Astrometry precisely measures an asteroid's position and speed. Polarimetry, on the other hand, analyzes polarized light reflected from its surface, providing clues about its texture and albedo.
By combining these techniques, researchers hope to develop more reliable models to anticipate an object's reactions in case of a deflection mission. This type of exercise helps better prepare the international community for the most critical scenarios.
Current calculations indicate that its 2089 passage will occur at about 3.7 million miles (6 million km), much farther than the 2025 one. However, on September 21, 2173, its trajectory should bring it to just 260,300 miles (418,900 km), a distance comparable to that separating us from the Moon.
Article author: Cédric DEPOND