Tech Desk 
Nov 30, 2024
A recently rediscovered asteroid, nicknamed Earth’s ‘second moon,’ briefly orbited our planet before continuing its journey through space. Measuring approximately 11.2 metres (37 feet) in diameter, this wandering asteroid, designated 2024 PT5, approached Earth on September 29, 2024. However, unlike our faithful natural satellite, the Moon, it left Earth’s orbit just two months later, on November 25, 2024.
This phenomenon captivated astronomers worldwide. Known as 2024 PT5, it has been studied extensively by scientists, including those at the Complutense University of Madrid. Among them, Carlos de la Fuente Marcos examined the asteroid's trajectory and suggested it might be a fragment of the Moon, dislodged by an ancient impact.
During its brief encounter with Earth, 2024 PT5 became a temporary member of the Arjuna asteroid group—a class of small celestial bodies that orbit the Sun at an average distance of 150 million kilometres.
Arjuna asteroids and gravitational capture
Arjuna asteroids are unique because they often travel at low speeds, which allows them to approach Earth closely. According to Fuente Marcos, objects that come within 4.5 million kilometres (2.8 million miles) of Earth at low speeds can sometimes be trapped by its gravity, albeit temporarily.
2024 PT5’s predicted return
The asteroid is predicted to return on January 9, 2025, passing at a distance of 1.8 million kilometres (1.1 million miles) from Earth. This time, however, it will be too far away and moving too quickly to be captured by Earth's gravity.
Over the past century, only two long-term asteroid captures have been recorded, making such events exceedingly rare. Short-term captures, like that of 2024 PT5, are more common, occurring roughly once a decade. Subsequent close approaches of 2024 PT5 are predicted for 2055 and 2084, offering astronomers future opportunities to study this intriguing celestial visitor.
