A mysterious object speeding through the solar system is accelerating in a way gravity alone cannot explain, fueling a theory that it could be a Soviet spacecraft lost nearly four decades ago.
Known as 1998 KY26, the roughly 36-foot-wide object is believed to be a near-Earth asteroid, but something other than gravity appears to be affecting its path. New research has now cast doubt on one explanation for what is pushing it through space.
"First of all, nothing is about to hit us, to be very clear on this," Isaacman said. "I've not seen any evidence to suggest this is a threat to our planet or anything other than an asteroid."
Scientists refer to KY26's unusual movement as "nongravitational acceleration," meaning something besides the pull of the sun and planets is affecting its path.
One theory has been that KY26 is a "dark comet" containing buried water that turns to gas and gives the object a push through space, even though astronomers have not detected the cloud or tail normally associated with a comet.
But a new peer-reviewed study by 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.
Isaacman said NASA continues to monitor KY26 but sees no reason for alarm.
"I have no reason to believe this is in any way remotely a threat to our planet or anything other than just an asteroid," he said.
Scientists may eventually get a definitive answer.
The Japan Aerospace Exploration Agency's Hayabusa2 spacecraft is scheduled to rendezvous with KY26 in July 2031, according to a 2025 study published in Nature Communications.
For Loeb, that encounter could provide the ultimate test of the Phobos 1 theory.
"Our prediction is that instead of an iceberg, Hayabusa 2’s cameras will reveal the label 'Made in the U.S.S.R.,'" Loeb wrote.