The key facts

  • Object 1998 KY26 (about 11 m) demonstrates non-gravitational acceleration near Earth
  • Avi Loeb and colleagues believe it may be the Soviet Phobos-1 station, lost in 1988
  • NASA, led by Jared Isaacman, stated that the object poses no threat to Earth

Unusual Acceleration of a Mysterious Object

An object designated 1998 KY26 is passing through the Solar System — a body about 11 meters wide, passing near Earth. Scientists have noticed that its trajectory cannot be fully explained by the gravitational pull of the Sun and Earth: forces of a different nature are acting on the object. Such behavior is called 'non-gravitational acceleration.' NASA head Jared Isaacman said on Thursday that the agency is tracking KY26, but emphasized: there are no grounds for concern, the object poses no known threat to Earth, and there is no evidence of a possible collision with our planet.

The Phobos-1 Hypothesis

Harvard astrophysicist Avi Loeb and his colleagues Adam Hibberd and Adam Crowl have put forward an unusual explanation: KY26 may be Phobos-1 — an unmanned Soviet station launched on July 7, 1988, which lost contact with Earth on its way to Mars. The researchers built a simplified model of Phobos-1 and compared how it would reflect sunlight while rotating with observations of KY26. The model matched well with eight separate sets of observations. KY26 reflects almost 52% of the sunlight falling on it and completes a full rotation in 5.35 minutes — in the opinion of the hypothesis's authors, these characteristics are consistent with the idea of an artificial object.

Alternative Explanations and Verification in 2031

The spacecraft hypothesis has competitors. According to a 2023 study, KY26 may be a so-called 'dark comet' containing trapped water, which turns into gas and creates thrust. However, astronomers have detected neither a cloud of gas nor a tail, which are characteristic of comets. Another study came to the opposite conclusion: 1998 KY26 is most likely a dehydrated asteroid, and water ice is unlikely to explain the acceleration, since temperatures are too high for a sufficient amount of ice to persist over a long period. Another possible explanation is the pressure of solar radiation on the object's surface. Other observations also point to a natural rocky asteroid: a study published in 2025 in the journal Nature Communications estimated its diameter at only 11 meters. The answer may come from the Japanese Hayabusa2 mission, which is scheduled to reach 1998 KY26 in July 2031 and study it at close range — this will be the first mission to directly examine an asteroid of such a small size. The resulting images and measurements will show whether it is a natural body or a potentially artificial object. Until then, Loeb's conjecture remains an interesting but unproven theory: the astrophysicist himself joked that Hayabusa2's cameras might detect the inscription 'Made in the U.S.S.R.' instead of a chunk of ice.