<p>Asteroid 1998 KY26 is accelerating in an unusual way, and one proposed explanation is that hidden ice is releasing gas and nudging it off course. But a temperature model described by science journalist Michelle Starr points to a problem for that idea: the small asteroid may be too warm to keep the ice for long.</p><p>Georgia Institute of Technology aerospace engineers Korbin Hansen and Masatoshi Hirabayashi modeled temperatures across KY26’s surface and interior using what is known about its size, orbit, reflectivity and likely composition. The asteroid is estimated to be about 11 meters across. Its trajectory shows unusual acceleration perpendicular to the plane of its orbit, while it rotates once every 5.35 minutes.</p><p>The proposed hidden-ice explanation is a version of the “dark comet” idea. Comets contain ice that can turn directly into gas and escape into space. That escaping material can provide a small extra push as a comet travels around the Sun. Dark comets are thought to release gas without producing the bright, visible tails commonly associated with comets, so they can look much like asteroids.</p><p>For buried water ice to survive over long periods, temperatures need to stay below about 145 kelvin, or minus 128 degrees Celsius. The model found that even KY26’s coldest regions average at least 212 kelvin, or minus 61 degrees Celsius, over the course of its orbit. That is cold by human standards, but warmer than the researchers’ threshold for long-term ice survival.</p><p>The report gives two conditional estimates from the model. If water ice made up 1 percent of KY26’s mass, it would disappear in a little more than 2,000 years. If that ice were responsible for the asteroid’s unusual acceleration, it would be gone in about 62 years. Those estimates make ice a less persuasive explanation, but they do not establish what is causing the acceleration.</p><p>There is a key uncertainty: researchers do not know how long KY26 has occupied its current orbit. It remains possible that the asteroid has ice if it has not spent long in its present location. The report says that possibility is shrinking, while noting an earlier paper that traced KY26 to a potential asteroid-belt origin.</p><p>Another possibility raised in the report is radiation pressure from sunlight. Sunlight exerts a small force, which may be enough to explain the asteroid’s apparent acceleration, but the available account does not settle the question. The Japanese space agency’s Hayabusa2 spacecraft is on its way toward KY26, with a rendezvous scheduled for July 2031. That encounter may provide a closer look at the object.</p><p>The temperature result narrows one explanation by testing whether the conditions needed for hidden ice are plausible. For now, the reported model leaves the source of KY26’s unusual motion unresolved.</p><p>Source: ScienceAlert report</p>