Could Earth have more than one 'moon'? Recently, scientists discovered a new 'quasi-moon' named 2025 PN7. This small asteroid orbits the Sun with Earth but does not orbit our planet directly. This revelation highlights the mysterious nature of our solar system.
What is a Quasi-Moon?
A quasi-moon is a type of asteroid that shares the Earth's orbital path around the Sun. It appears to be a moon but is actually in the Sun's orbit, showcasing the playful dance of gravity. According to the Planetary Society, these asteroids accompany Earth temporarily, not forever.
Earth already hosts seven known quasi-moons, such as Kardia and Kamooalewa. The newly found 2025 PN7 is the smallest and least stable of them. It will journey with Earth for another 60 years before departing.
Source: aajtak
How Was 2025 PN7 Discovered?
The asteroid was first observed on August 2, 2025, by the Pan-STARRS1 telescope at Hawaii's Haleakala Observatory, although archival data shows it has been visible since 2014. French journalist and amateur astronomer Adrien Coffinet was the first to analyze it, declaring it Earth's quasi-satellite on the Minor Planet Mailing List on August 30.
Co-author of the study from the Complutense University of Madrid, Carlos de la Fuente Marcos, noted it was too small and faint to be noticed until now. The discovery was published on Research Notes of the American Astronomical Society on September 2, 2025. The International Astronomical Union issued a circular about it on August 29, using data from July 30.
Features and Dimensions of 2025 PN7
At just 19 meters (62 feet) in diameter, 2025 PN7 is slightly smaller than the meteor that struck Chelyabinsk, Russia, in 2013. Its brightness is at magnitude 26, making it extremely dim. For comparison, stars visible to the naked eye are magnitude 6 or less. Sirius, the brightest star, is at -1.5. Thus, only advanced telescopes can detect it.
This asteroid ranges from 4.5 million to 60 million kilometers from Earth and originates from the Arjuna asteroids. Its speed suggests it is a captured asteroid, resonating 1:1 with Earth's orbit, meaning it circles the Sun simultaneously with us.
Source: aajtak
Why Has It Remained Hidden for So Long?
Its small size and dim appearance made it difficult to see from Earth for decades. However, new tools like the Vera C. Rubin Observatory can now find such objects. This asteroid has been accompanying Earth since the 1960s, approximately 60 years. While it poses no danger, it serves as a rich target for scientific study.
What Does the Future Hold?
More quasi-moons like 2025 PN7 could be discovered in the future, with the Rubin Observatory set to make significant findings. The most famous quasi-moon, Kamooalewa (2016 HO3), is 40-100 meters in diameter. China's Tianwen-2 mission, launching in May 2025, aims to collect samples from it by 2027, offering insights into the solar system's origins.
The Difference Between Quasi-Moons and Mini-Moons:
Mini-moons temporarily get captured in Earth's orbit for weeks or months, while quasi-moons remain for decades.
