Earth is set to welcome a special guest this fall, albeit temporarily. This celestial visitor, known as 2024 PT5, is described as a “mini moon” and will orbit our planet for just under two months. The excitement around this event is palpable within the astrophysics community as scientists prepare to study this asteroid up close.
Expected to arrive on September 29 and stay until November 25, the mini moon is not your average celestial body. Measuring about 33 meters, it’s similar in size to a school bus, making it relatively small compared to the natural moon we are accustomed to. Casey DeRoo, an associate professor from the University of Iowa’s Department of Physics and Astronomy, explained the significance of this occasion. “We find these kinds of asteroids with telescopes tasked with surveying the entire sky,” he noted.
Asteroids like PT5 belong to a category referred to as near-Earth objects. Remarkably, there are around half a billion of these rocky bodies located within close proximity to Earth. Although many pass by without consequence, capturing one—however briefly—is quite rare. Typically, these mini moons can linger for much longer; for example, the last recorded mini moon, known as 2020 CD3, remained with Earth for over two years before drifting back out to space.
Asteroid 2024 PT5 has roots tracing back to the group of asteroids adjacent to Earth known as the Arjuna asteroids. These differ from most asteroids, which are primarily found between Mars and Jupiter, sitting instead at distances much closer to our home planet. While PT5’s exact composition is still under scrutiny as it draws near, its arrival opens the door for various upcoming research opportunities.
"One exciting aspect of capturing these near-Earth objects is the possibility of sending missions for exploration or, potentially, even resource mining," said Hai Fu, another associate professor at the University of Iowa. This prospect of resource extraction from asteroids has ignited conversations about future exploratory missions. Fu described this period as the “early stage of an exciting new field” of research.
According to experts, to be classified as a mini moon, such objects must approach Earth slowly and remain within its gravitational pull. 2024 PT5 will not complete a full orbit around our planet; instead, it will trace more of a horseshoe-shaped path before being slung back toward the depths of space. DeRoo predicts this temporary moon may return to our vicinity once again, but not for about 30 years.
While many are eager to catch a glimpse of the mini moon, reality dictates otherwise. PT5 is expected to be invisible to the naked eye and even through standard telescopes usually found in backyards. To spot such dim celestial objects, astronomers would employ more specialized equipment. For reference, the largest telescope available at the University of Iowa’s Van Allen Observatory measures 17 inches. Swirbul, the observatory manager, estimates you would need equipment nearly double this size to observe PT5.
Nevertheless, the event isn’t without merit for researchers, and those collecting data on the mini moon will be taking advantage of current technology to monitor its presence and characteristics. Projects like the Asteroid Terrestrial-impact Last Alert System (ATLAS), funded by NASA, have been pivotal for monitoring near-Earth objects, and 2024 PT5 is no exception. This technology allows scientists to detect potential threats well before they approach, offering at least five years of lead time to prepare.
DeRoo underscored the importance of early detection and monitoring. “We know enough about them now to have ample warning before any possible collision,” he stated confidently. The precision with which scientists can observe and interpret the behaviors of these asteroids could prevent future calamities.
Filipa Santos Sousa, another astronomy expert, pointed to the rarity of the event, accentuating how many factors come together to allow for such orbital capture. Sousa mentioned, “The asteroid needs to approach Earth slowly and be within about 4.5 million kilometers to qualify.”
Initial findings about PT5 were made possible thanks to persistent observational efforts, which helped track this minuscule yet fascinating object. According to the study published titled “A Two-month Mini-moon: 2024 PT Captured by Earth from September to November,” it is predicted not to be visible through amateur telescopes, especially from observatories located in areas with high light pollution, such as various urban settings, including cities across Portugal.
Even though Earth’s newest mini moon will be inaccessible to observation for the average onlooker, the scientific community embraces this opportunity. Asteroids offer invaluable insights about the history and evolution of the solar system, allowing researchers to measure their compositions, trajectories, and potential resources, which could be exploited on future missions.
To recap, Earth’s 2024 PT5 is set for its orbital dance with our planet later this month. The asteroid will rotate around us briefly, leaving before making its slow return to its original orbit around the sun. Harrington, another linked researcher, asserted, “This presents itself as both a remarkable phenomenon and as the future of space exploration.”
Throughout history, many mini moons have made temporary appearances, the most recent being 2020 CD3. It serves to remind us of the dynamic and ever-evolving nature of our cosmic environment. And even if we can’t see it with our eyes, 2024 PT5’s visit is anticipated with great curiosity and scientific ambition.
