The Phobos 1 Hypothesis
Harvard astrophysicist Avi Loeb and researchers Adam Hibberd and Adam Crowl have examined whether KY26 could actually be Phobos 1, an unmanned Soviet spacecraft that stopped communicating while traveling to Mars in 1988.
KY26 is about 36 feet across, reflects roughly 52% of the sunlight that hits it and completes a full rotation every 5.35 minutes.
The researchers built a simplified model of Phobos 1 and compared the way it would reflect sunlight as it spun with observations of KY26. They found the spacecraft model closely matched eight sets of observations of the object.
They also tested whether sunlight pushing against a cylinder or solar panels could help explain KY26's movement and found the model better matched hundreds of telescope and radar observations.
"Although an investigation of this kind cannot be conclusive," the researchers wrote, the findings "add strong weight to the Phobos 1 hypothesis."
The researchers stressed, though, that their model does not prove KY26 is the missing spacecraft, describing the theory as "strongly plausible but presently unproven."
Other research points to a more conventional answer. A separate study published this year in Astronomy & Astrophysics examined the light reflected by KY26 and found its makeup appears consistent with a type of rocky asteroid. Researchers concluded it likely came from the inner part of the asteroid belt.