Pan-STARRS 1 detected the asteroid now called 2025 PN7 on 2 August 2025. Within weeks, orbital calculations showed that the tiny object had already been travelling in step with Earth for about 60 years.
It had not gone entirely unseen. Telescopes had recorded it in older images, but no one knew that those faint points belonged to an Earth quasi-satellite until the 2025 observations provided an orbit that could be traced backwards.
The distinction matters: 2025 PN7 is not a second moon. It orbits the Sun rather than Earth, while moving through a temporary 1:1 resonance that keeps its average pace close to ours.
The discovery reached backwards through the archive
Carlos de la Fuente Marcos and Raúl de la Fuente Marcos reported the object in a short 2025 Research Notes of the AAS paper, “Meet Arjuna 2025 PN7, the Newest Quasi-satellite of Earth”. When they wrote it, the calculated orbit rested on 27 observations spanning 4,279 days, nearly 12 years.
That span is possible because astronomy has a word for finding an object before its discovery: precovery. Once enough recent observations reveal an orbit, software can calculate where the object should appear in older exposures. Researchers can then return to the archive and inspect a very small patch of an old image rather than searching the whole sky again.
A Dark Energy Camera exposure from 17 November 2018 shows the problem clearly. 2025 PN7 is present as a faint dot surrounded by stars, stray pixels and cosmic-ray streaks. The image contained the evidence, but not yet the identity.
JPL’s database has continued to change as observations have accumulated. Its August 2026 orbital solution uses 36 measurements, with the earliest dated 11 December 2013 and the latest from 6 August 2026. The asteroid was photographed years before its announcement; the difficult step was connecting separated detections to the same moving body.
Why it looks like a satellite without being one
A genuine moon travels around a planet inside that planet’s gravitational domain. A temporary mini-moon does the same for a limited period. A quasi-satellite remains on a heliocentric orbit, but its average period around the Sun matches the planet’s closely enough to produce a recurring pattern in the planet’s sky.
Current JPL data for 2025 PN7 give it an orbital period of about 366 days, a semimajor axis of 1.001 astronomical units and an inclination just under two degrees. Its path is slightly more elongated than Earth’s, with an eccentricity of about 0.108.
From a Sun-centred view, Earth and the asteroid follow separate orbits. In a frame that rotates with Earth, however, 2025 PN7 appears to loop around our planet over time. That apparent looping relationship is the quasi-satellite state.
Earth does not own this object.
The 60-year history is a model, not a photograph
The archival images and the long dynamical history are related, but they are not the same evidence. Photographs now establish a measured arc back to 2013. The claim that 2025 PN7 has accompanied Earth since the 1960s comes from integrating its orbit backwards under the gravitational influence of the Solar System.
The de la Fuente Marcos paper calculated a total residence of about 128 years in the present quasi-satellite state, compared with roughly 381 years for Kamo’oalewa. The published integrations place 2025 PN7’s entry around the mid-1960s and imply that the state should persist for roughly another six decades before its relative motion changes.
The 128-year estimate comes from one short orbital study, not settled consensus about exact entrance and exit dates. Small asteroids are affected by more than planetary gravity, including weak thermal forces, and every additional observation can refine a projection. The defensible conclusion is broad: this resonance began decades before discovery and it is temporary.
Faintness, not distance alone, kept it hidden
The European Space Agency’s NEO Coordination Centre places 2025 PN7 in a size range of about 14 to 30 metres. Its absolute magnitude is about 26.3, and ESA lists its useful observing window as July through September. Even near its brighter opportunities, it remains a telescope target rather than something anyone could pick out by eye.
Its small size also changes the risk context. JPL lists 2025 PN7 as a near-Earth Apollo asteroid, but not as a potentially hazardous asteroid. The story is orbital classification and detection, not an overlooked impact threat.
That is quite different from Apophis and its exceptionally close 2029 passage, where the object is hundreds of metres wide and the encounter will measurably alter its orbit and possibly its surface.
An archive can become a second survey of the sky
Automated surveys are usually described as machines for finding what is there tonight. 2025 PN7 shows their other function. Each calibrated exposure becomes a dated record that can be searched again when a newly calculated orbit provides the right coordinates.
Precovery extends an observation arc, reduces orbital uncertainty and makes numerical integrations less dependent on a short run of fresh detections. Here, a discovery made in August 2025 acquired nearly 12 years of observational history because earlier surveys had preserved what they saw.
More astrometry will continue to refine the orbit. Physical questions are less settled: astronomers still need observations of the asteroid’s colour, rotation and composition before its origin can be assessed with similar confidence.