The Earth is unique in our solar system as a thriving, habitable world. Yet, we’re not entirely alone; we frequently receive visitors, often in the form of asteroids. Some of these space rocks even decide to linger for a while, temporarily earning the title of a ‘moon-like’ companion.
The latest of these fleeting guests is an asteroid known as 2025 PN7. Discovered this summer, its orbital path around the sun closely mirrors Earth’s, much like a car traveling in the same lane on a cosmic highway. This type of object is called a quasi-moon, and it’s speculated that 2025 PN7 might be the smallest one ever observed, potentially measuring less than 52 feet – shorter than a standard bowling lane.
The origins of asteroids near Earth vary. Some journey from the main asteroid belt located between Mars and Jupiter, while others are fragments of our own Moon, blasted into space by powerful meteorite impacts. With limited telescopic observations of 2025 PN7, its exact origins remain a mystery, prompting scientists to engage in fascinating speculation.
What is certain, however, is that this tiny asteroid is merely a transient visitor.
2025 PN7 belongs to a small group of space rocks that briefly accompany, precede, or follow Earth in its solar orbit. Like its fellow cosmic travelers, this asteroid will eventually depart, heading deeper into space after approximately 60 years.
Earth is host to several such celestial companions, categorized as mini-moons or quasi-moons. Mini-moons, unlike quasi-moons, actually orbit our planet. But they make for fickle fans: They tend to swing around Earth for only a few months. For instance, asteroid 2024 PT5 briefly orbited Earth last autumn before continuing its independent journey by late November.
Unlike their fickle mini-moon counterparts, quasi-moons remain in orbit around the sun, closely synchronized with Earth’s path. These more committed companions can stay aligned with Earth’s orbit for hundreds or even thousands of years. This prolonged proximity makes them prime candidates for scientific study and future planetary missions. For example, another known quasi-moon, Kamoʻoalewa, is the target of China’s Tianwen-2 mission, which aims to collect a geological sample for return to Earth.
Astronomers first identified 2025 PN7 on August 2nd using the Pan-STARRS observatory in Hawaii. Subsequent analysis of archival images, some dating back several years, allowed researchers to meticulously plot its precise orbital trajectory.
It appears that 2025 PN7 settled into its quasi-moon orbit around 1957, coincidentally just as humanity launched its first artificial satellite, Sputnik 1.
Scientists estimate that in August 1980, 2025 PN7 passed within 2.5 million miles of Earth – a distance roughly ten times that between Earth and its natural moon. At its furthest point, this quasi-moon can be as far as 11 million miles away.
Simulations indicate that 2025 PN7 will reside in Earth’s solar orbit for a total of 126 years. By 2083, it is predicted to break away and relinquish its quasi-moon status.
The title of ‘tiniest quasi-moon’ for 2025 PN7 is still provisional. Estimating an asteroid’s size typically relies on how much sunlight its surface reflects, but 2025 PN7’s elusive nature has made accurate observation challenging. Its true dimensions remain uncertain, though it could be up to 160 feet long. Future observations will be crucial to confirm whether it retains its record as the smallest known quasi-moon.
Regardless of its exact size, the discovery of 2025 PN7 is exciting for astronomers. Near-Earth asteroids, particularly those that don’t pose a collision threat, provide invaluable insights into the formation and evolution of our inner solar system. As one researcher noted, “It is even cooler when they get captured and they stay close to the Earth for quite some time.”