A previously undetectable asteroid, classified as a “quasi-satellite” of Earth, was recently identified after having remained close to our planet for around 60 years. The object, named 2025PN7, is a rocky mass approximately 30 meters in diameter, which has been observed for 25 years since its formal discovery. Its long stay and the difficulty in detecting it raise fascinating questions about the celestial bodies that share Earth’s orbital neighborhood.
The nature of quasi-satellites and their particularities
Unlike moons that directly orbit a planet, quasi-satellites are asteroids that, although they revolve around the Sun, maintain an orbit very close to that of a planet, accompanying it on its stellar journey. O 2025PN7, por exemplo, completa sua volta ao redor do Sol em um período similar ao da Terra, cerca de um ano. This characteristic distinguishes it from “mini-moons”, which are objects temporarily captured by Earth’s gravity, as was the case with 2024PT5, which was in Earth’s orbit for just two months in 2024.
Details about the identification and size of 2025PN7
2025PN7 was detected on August 29, 2025, using the Pan-STARRS telescope, located on Mount Haleakala, Hawaii, United States. Further analysis of archived data revealed that the asteroid had been following a similar trajectory to Earth for decades. The reason for its late discovery, according to Carlos de la Fuente Marcos, researcher at the Complutense University of Madrid and one of the study’s authors, was its small size, making observation difficult.
2025PN7’s diameter is estimated to be approximately 30 meters, but other analyzes suggest it could be as small as 19 meters. By comparison, the Christ the Redeemer Statue in Rio de Janeiro is about 30 meters tall, making the scale of the asteroid more tangible. This size makes it the smallest quasi-satellite ever identified, revealing that the solar system still holds many surprises in its complexity.
The scientific potential and the importance of continuous research
The discovery and study of quasi-satellites like 2025PN7 are crucial to deepening our knowledge of the universe and the formation of the solar system. These objects offer a unique window into understanding orbital dynamics and the origin of space debris. The existence of such a small quasi-satellite suggests that the lower size limit for these bodies may be even smaller than previously thought.
Furthermore, the exploration of these asteroids could open up new opportunities for space exploration. They are considered relatively accessible targets for unmanned probes and can serve as testing grounds for future technologies and sample collection. The Chinese Tianwen-2 probe, launched in May, has as one of its objectives the Kamo-o-arewa quasi-satellite, which is believed to be an ancient lunar fragment, scheduled to return in 2027.
Orbital characteristics and safety for the planet
2025PN7 has an orbit that can vary between a circular trajectory close to Earth or a horseshoe shape, in which its distance from our planet can reach up to 297 million kilometers. It is predicted to remain close to Earth for another six decades before being influenced by solar gravity and returning to a more distant orbit.
It is important to highlight that, despite their proximity, quasi-satellites and mini-moons generally do not pose a risk of collision with Earth. Therefore, 2025PN7 is not considered a threat. Most of these objects are composed of natural rocks, and modern observation technologies make it possible to distinguish between celestial bodies and artificial debris, such as ancient satellites.
Scientists also speculate that 2025PN7, along with 2024PT5, may belong to the “Arjuna group of asteroids.” This group is characterized by rocky asteroids with orbits similar to Earth’s, but which are not part of the main belt between Mars and Jupiter. There is a theory that fragments from past lunar collisions may have been ejected and integrated into the Arjuna group, reinforcing the connection between these objects and the history of our own Moon.
The inexhaustible frontier of astronomical knowledge
The continuous search for new objects in the solar system reaffirms that our universe is full of discoveries to be made. Each quasi-satellite or mini-moon found adds a piece to the complex puzzle of planetary formation and celestial dynamics. Observation technology, increasingly improved, promises to reveal even more secrets from the “corners” of our solar system, constantly expanding the limits of our knowledge.