Earth is set to play host to a “mini-moon” this week, as a small asteroid about the length of a double-decker bus enters the planet’s orbit. The temporary guest, called 2024 PT5, is set to arrive on September 29 and is expected to befriend the regular Moon for around two months.
Daniel Brown, associate professor in astronomy at Nottingham Trent University, explained that a mini-moon is a small object orbiting another solar system body, which could be either just a rock, known as an asteroid, or a mixture of rock, dust, and ice, termed a comet. In either case, these objects do not orbit around Earth forever but for a short amount of time.
2024 PT5, belonging to the Arjuna asteroid belt, was first discovered in August last year, the day before it approached Earth at a distance of 353,200 miles (568,500 km). It is expected to orbit Earth for 57 days before eventually swinging out of the planet’s gravitational pull due to its excess energy.
Although a temporary visitor, Earth will likely encounter this mini-moon again, as scientists predict it will be captured by Earth’s gravity in 2055. This event illustrates the complex orbits of small bodies in the solar system, briefly interacting with Earth before continuing on their path around the Sun.
This phenomenon is not new, as Earth previously hosted a mini-moon four years ago, named 2020 CD3, which orbited the Earth for over a year. Notably, 2024 PT5 will not be visible to the naked eye and can only be observed using telescopes employed by professional astronomers.
Daniel Brown noted that mini-moons are fairly common, but observing them is challenging due to their small, faint, and fast-moving nature. 2024 PT5 is categorized as a near-Earth object (NEO), a group of space rocks that regularly pass by Earth. While astronomers monitor NEOs as a precaution against potential threats to Earth, experts believe that 2024 PT5 is unlikely to pose any danger.
The mini-moon’s arrival offers a unique opportunity to study and understand the dynamics of these celestial bodies interacting with Earth’s orbit, shedding light on the complexities of our solar system.