Astronomers are investigating the asteroid 1998 KY26 after observing an unexplained acceleration perpendicular to its orbital plane.
The 11-meter object, which completes a full rotation every 5.35 minutes, exhibits movement patterns that traditional gravitational models cannot fully account for.
The anomaly challenges existing theories regarding small solar system bodies. While scientists can typically predict trajectories using solar gravity, planetary pull, and solar radiation pressure, this specific asteroid’s path deviates from those expected calculations.
Thermal instability challenges comet theory
Researchers initially proposed that 1998 KY26 might be a “dark comet.” This category includes objects that release gases through sublimation—a process where frozen material turns directly into gas—without creating the massive, bright tails seen in traditional comets. This gas expulsion would act like a small rocket engine, providing the thrust needed for the observed acceleration.
However, a new study published in the journal Icarus suggests this explanation is physically unlikely.
The model indicates the asteroid is too warm to sustain the ice required for comet-like behavior. Even the coldest regions of the body maintain average temperatures of at least 212 Kelvin, or approximately 61 degrees Celsius below zero.
To remain stable over long periods, buried ice would need temperatures below 145 Kelvin, or 128 degrees Celsius below zero. The study shows a large discrepancy in the math:
- If ice accounted for only 1 percent of the asteroid’s mass, it would vanish in just over 2,000 years.
- If the ice volume were high enough to generate the observed acceleration, the reserves would deplete in only 62 years.
Because 1998 KY26 is likely billions of years old, the researchers noted it is difficult to reconcile such a rapid depletion with the object’s known age. While it is possible the asteroid recently entered a warmer region of space, other research suggests the object originated in the asteroid belt, further weakening the comet hypothesis.
Solar radiation and thermal emission drive trajectory changes
If gas expulsion is not the driver, scientists are looking at alternative physical forces. One possibility involves solar radiation pressure. For a small, lightweight body of only 11 meters, the momentum transferred by photons hitting the surface can accumulate into a measurable change in trajectory.
Thermal emission is another factor under scrutiny. As the sun heats the surface, the resulting release of energy in different directions can create a subtle push.
JAXA Hayabusa2 encounter timeline
Direct observation remains the only way to resolve the mystery of the asteroid’s acceleration. The Japan Aerospace Exploration Agency (JAXA) has already positioned a spacecraft to investigate the object. The Hayabusa2 probe, which previously sampled the asteroid Ryugu, is currently in an extended mission phase.
The spacecraft is scheduled to encounter 1998 KY26 in July 2031. This close-range study aims to provide precise data on the asteroid’s shape, composition, and surface properties to determine what is actually driving its unusual movement.
Until that encounter, the origin of the perpendicular acceleration remains an open question in planetary science.
