On October 29, 2026, the Minor Planet Center (MPC) assigned the provisional designation "2026 QQ8" to a small body discovered near Earth and issued an observation circular. The next day, it explained how it had concluded that the object is natural. Observers had been tracking the object under the identifier "Sar2901." In September, opinion was divided over whether it was an artificial object such as space debris or a natural one, and the designation had been put on hold. Two things supported the latest decision: position data built up through additional observations, and an estimate of the effect of solar radiation pressure derived from that data. Still, whether an object is temporarily captured by Earth's gravity and whether it is natural or artificial are separate questions.
From a Delayed Designation to the Identification of 2026 QQ8
In its September 3 newsletter, the MPC said it would withhold a provisional designation for Sar2901. The object was first observed on August 19, but the fact that it was moving in an orbit close to Earth was not enough to tell whether it was natural or artificial. Both possibilities remained open at the time, and additional observational data were needed to decide.
The MPC then issued the observation circular "MPEC 2026-U95" at 16:50 UT on October 29. In its explanation the following day, it said that additional observations had extended the observation arc and made it possible to estimate the effect of solar radiation pressure. As a result, an artificial origin was ruled out and the object was judged to be natural. The circular also states that no association with any known artificial object was found. In other words, the announcement does not describe the discovery of a new object. It means that, for an object found in August, the evidence needed to judge its origin has now come together.
On the object's relationship with Earth, MPEC 2026-U95 reports that orbital integration shows the object to be temporarily bound to Earth by gravity. Orbital integration is a method of numerically calculating an object's motion over time from observed position data. In its October 30 explanation, the MPC also said that 2026 QQ8 is most likely a temporary "mini-moon" of Earth. However, October 29 is only the date the circular was issued, not the date Earth's capture began.
How Sunlight Helps Distinguish Space Junk from Natural Objects
Sunlight exerts a slight push on objects. This force, produced when photons transfer momentum to an object, is called solar radiation pressure. It acts on natural asteroids as well as on satellites and rocket debris, but its effect varies with an object's mass and shape. According to an explanation from NASA's Jet Propulsion Laboratory (JPL), a hollow rocket upper stage has more surface area per unit mass than dense rock, so it is more strongly affected by solar radiation pressure.
An important indicator for examining this difference is the area-to-mass ratio: the effective area that receives light divided by mass. The larger the value, the more surface area an object has relative to its mass, and the more easily solar radiation pressure changes its orbit. By continuously measuring an object's position and adjusting an orbital model that accounts for solar radiation pressure until it matches the observations, this ratio can be estimated. It is not, however, a method for directly measuring the mass or surface area of a distant object.
The area-to-mass ratio estimate given in the observation circular for 2026 QQ8 was (7.94 ± 3.41) × 10⁻⁴ m²/kg, with the uncertainty given as 1σ (one standard deviation). This value is a physical quantity derived from an orbital model, not a probability that the object is natural. The MPC used the solar radiation pressure estimate as evidence for its natural-object judgment, but the circular gives no numerical threshold for uniformly separating natural from artificial objects.
The analysis covers a single object, 2026 QQ8, and the circular includes position data from August 19 to October 9. The basic flow of the work was telescope position observations, estimation of the area-to-mass ratio using an orbital model, and a judgment of origin based on that result. No experimental conditions were manipulated to measure the object's properties, and the result is not a direct analysis of its composition.
Follow-Up Observations in September and October Supported the Decision
The MPC had held off on assigning a designation as of September 3, but the October 29 circular also includes records of later observations made on September 5, September 19, and October 9. These follow-up observations provided about seven weeks of position data from the time of discovery in August. Arranging the MPC newsletters and circular in chronological order shows how the decision came about.
| Date (2026) | Observation / announcement | Source |
|---|---|---|
| August 19 | Discovery observation by Hungarian observatory K88 | MPEC observation table |
| September 3 | MPC explains it is withholding a provisional designation for Sar2901 | MPC September issue |
| September 5 | Additional observation by G37 | MPEC observation table |
| September 19 | Additional observation by G37 | MPEC observation table |
| October 9 | Additional observation by T12 | MPEC observation table |
| October 29 | MPC issues MPEC 2026-U95 | MPEC observation circular |
| October 30 | MPC explains how it judged the object to be natural | MPC October issue |
Observatory code G37 refers to the 4.3-meter Lowell Discovery Telescope, and T12 to the University of Hawaii's 2.24-meter (88-inch) telescope on Maunakea. In its September newsletter, the MPC had indicated that the fading Sar2901 would be observable again from mid- to late November. In fact, however, additional observations were made earlier, in September and October, and that data was included in the October 29 circular.
According to the MPC's October explanation, the extended observation arc from the G37 and T12 follow-up observations is what made the solar radiation pressure estimate possible. However, the data in the circular are not a record of continuous measurements and do not necessarily cover every observation made. How much each individual observation contributed to the improved precision has also not been disclosed. What can be confirmed is that the position data added after the September decision to withhold the designation led to the October judgment that the object is natural.
Temporary Capture by Earth and a Natural-Object Determination Are Separate Issues
A precedent for investigating the origin of a temporarily captured object is "2020 SO," discovered in 2020. In November of that year, JPL reported that more than 170 position measurements over three months had clearly revealed the effect of solar radiation pressure, indicating that the object had low density. In its December 2 announcement, JPL combined calculations tracing the past orbit with spectroscopic observations from NASA's Infrared Telescope Facility (IRTF) and confirmed that the object was the upper stage of a Centaur rocket launched in the 1960s. In that case, orbital analysis was used to infer the object's nature, and separate evidence was then used to identify it as artificial. However, the observation periods and measurement precision of 2020 SO and 2026 QQ8 may differ, so the former's results cannot simply be applied as a criterion for the latter.
Objects temporarily captured by Earth like 2026 QQ8 also need to be distinguished from "quasi-satellites." According to an explanation from Lowell Observatory, a quasi-satellite is an object that orbits the Sun while remaining relatively close to Earth. For 2026 QQ8, by contrast, the MPC's orbital integration showed a state in which the object is temporarily bound by Earth's gravity. Both show characteristic motion near Earth, but their dynamical states differ, and the phrase "little moon" alone cannot tell them apart accurately.
The announcement is also based on an MPC observation circular and explanation, not on a peer-reviewed original paper. Although data were gathered from multiple observatories, no spectroscopic results directly examining the composition of 2026 QQ8 have been reported, nor any verification by an independent research team. The fact that several observatories tracked the same object should be distinguished from the object's origin having been verified by independent studies.
In the circular, the MPC strongly urges further observations and dynamical studies of 2026 QQ8. Acquiring additional position data to refine orbit calculations may make it possible to understand the motion of objects temporarily captured by Earth in greater detail. With the natural-object judgment in place, determining what orbit 2026 QQ8 will follow near Earth is the next research task.