What happened
In 1998, an astronomer at the University of Arizona discovered 1998 KY26, an object that looked like an asteroid but moved with an acceleration of its own, greater than what the Yarkovsky effect explains, the thermal force caused by the Sun’s radiation. For years it was thought to be a dark comet, a comet with no visible tail. A new study from the Georgia Institute of Technology rules that out.
Why it matters
The cometary explanation needs ice: when ice sublimates it turns to gas and pushes the object like a rocket. If 1998 KY26 cannot have ice, something else is accelerating it, and there is still no answer. Understanding these objects matters because predicting the path of nearby asteroids depends on knowing the forces that move them.
The number
For ice to survive inside an object, the temperature must be below -128 °C; the team’s calculation indicates that even in its coldest spots the asteroid does not drop below -61 °C.
Context
Nobody stuck a thermometer in the asteroid: the calculation is indirect, with models that use known data. It is known to be about 11 meters across and to rotate once every 5.35 minutes, and its reflectivity and likely composition are known. From that its temperature was estimated. Dark comets release little gas and dust, either because they are small or because they have little dust on the surface, which is why they are barely visible. With this temperature, 1998 KY26 does not fit that category. On related topics, Mamífero published Deflecting an asteroid with X-rays depends on the side; The Sun eroded 1.7 to 5.2 m of comet 3I/ATLAS; Coffee and less dementia after 43 years of follow-up and Webb finds deuterium-rich methane in 3I/ATLAS.
What’s next
Scientists will have to look for other explanations for the acceleration or measure the object up close. The question remains whether another physical mechanism explains its motion.
Bottom line
It is a good example of how a negative result, ruling out a hypothesis, also moves science forward.
Sources
- Xataka, report on the Georgia Institute of Technology study (accessed November 9, 2026).
- Cover image: Kestrel, CC BY-SA 4.0, via Wikimedia Commons
Edited by Rodrigo Cornejo. How we select and verify: who writes these notes.
