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An 11-meter space rock known as 1998 KY26 is accelerating in its orbit without a clear explanation from gravitational forces alone, according to a study published in the scientific journal Icarus.
Discovered in 1998, the tiny celestial body measures about 36 feet across. Researchers have tracked its movements for over twenty-five years, noting an unexpected extra push that gravity from the Sun and planets cannot fully account for. El Confidencial reported that the object completes one full rotation every 5.35 minutes, based on radar measurements and astronomical observations published in Nature Communications in 2025.
Scientists previously suggested that the object might be a dark comet carrying hidden water ice beneath its surface. Solar heat would convert that ice into gas, creating the propulsion that alters its trajectory. However, recent thermal modeling challenges that hypothesis.
High Temperatures Prevent Water Ice from Surviving
Their findings indicate that temperatures are simply too high for water ice to survive for long periods. Even the coldest regions reach roughly 212 kelvin, which is about 61 degrees below zero Celsius, as El Pespunte noted.
Calculations show that if ice made up just one percent of the object’s mass, it would vanish in roughly two thousand years. Marca usa reported that if gas release drove the acceleration, those reserves would deplete in a mere 62 years.
DW.com said that solar radiation pressure and thermal emission might contribute to the anomalous movement. Earlier studies indicated those radiation effects by themselves seemed insufficient to explain the full magnitude of the observed acceleration.
The Soviet Space Probe Hypothesis
Harvard astrophysicist Avi Loeb proposed an entirely different explanation for the acceleration. He suggested that 1998 KY26 might actually be Phobos 1, a Soviet spacecraft launched toward Mars in 1988 that lost contact with Earth before completing its mission.
Loeb and his collaborators believe the physical characteristics, brightness, and movement of the object could match the lost spacecraft. Reflected sunlight on metallic surfaces and solar panels could create enough radiation pressure to explain the unusual movement.
Marca usa reported that the hypothesis remains unconfirmed, and the object could still turn out to be a natural asteroid.
The Hayabusa2 Mission in 2031
The Japan Aerospace Exploration Agency already has a spacecraft on the way to investigate the object directly. The Hayabusa2 probe, which previously gathered samples from the asteroid Ryugu in 2019, is scheduled to reach 1998 KY26 in July 2031.
The upcoming encounter will give researchers a close-up view of its structure and composition. DW.com reported that the mission will offer new clues about the nature of the object and the forces altering its trajectory.
The encounter is set for July 2031.
