The coldest parts of 1998 KY26 may still be too warm for buried ice to last. A new temperature study puts those regions above -77 degrees Fahrenheit, raising questions about whether escaping water vapor drives the acceleration of the mysterious object that Japan’s Hayabusa2 spacecraft is heading toward.
Asteroids and comets can accelerate without anything unusual happening. What scientists haven’t worked out here is where the additional push comes from, ScienceAlert reports. A study published in Icarus examines whether the answer could be that 1998 KY26 is a “dark comet.”
Though they act like rocky asteroids, dark comets show acceleration that gravitational forces can’t fully explain. Ice turning directly into gas and escaping into space can supply the extra thrust.
Georgia Institute of Technology aerospace engineers Korbin Hansen and Masatoshi Hirabayashi tested that possibility by building a temperature model from existing data. The object measures 36 feet and turns once every five and a half minutes. According to the source report, it is 186 million miles from Earth.
Those modeled temperatures make an ice-based explanation difficult. Buried reserves capable of sustaining thrust from escaping water wouldn’t last, even in the object’s coldest regions.
“Our temperature model results indicate that the water outgassing rate on 1998 KY26 would be too high to maintain buried ice, refining the understanding of the asteroid’s composition,” Hansen and Hirabayashi wrote.
At those temperatures, an ice supply powering the acceleration through sublimation would be exhausted in just 62 years. As ScienceAlert points out, that is a brief span compared with the object’s suspected age of billions of years. If this explanation were correct, the ice would have disappeared long ago.
The researchers therefore conclude that “1998 KY26 is likely a dehydrated asteroid,” which probably shed its water reserves long ago. Solar radiation pressure or “thermal emission forces” might instead provide the push. Neither possibility, however, has been established as the answer.
A different proposal comes from Harvard astronomer Avi Loeb, who suggests the object is a derelict Soviet spacecraft launched almost 40 years ago. This temperature research doesn’t confirm his suggestion. Rather, it questions ice as the source of the acceleration while leaving the force behind 1998 KY26’s motion unresolved.
Hayabusa2, operated by the Japanese space agency, is expected to reach the object for a rendezvous in July 2031. Scientists could then get a firsthand view of what is happening.
