An object that has been orbiting the Sun for decades and was long believed to be an asteroid could actually be a Soviet spacecraft that went missing nearly 40 years ago, a Harvard scientist has suggested.
The object, known as 1998 KY26, is approximately 11 metres (36 feet) across and completes a rotation every 5.35 minutes.
However, what has puzzled scientists is its unusual acceleration, which cannot be explained by the gravitational pull of the Sun and planets alone.
Researchers previously suspected the object was a “dark comet”, meaning it could be releasing gas without producing a visible tail.
A new study by aerospace engineers Korbin Hansen and Masatoshi Hirabayashi at the Georgia Institute of Technology has cast doubt on that explanation.
Published online in the journal Icarus, the study found that the object is too warm to retain the water ice needed to produce such an acceleration.
Harvard astrophysicist Avi Loeb, however, believes the object could be Phobos 1, a Soviet spacecraft launched on July 7, 1988, to study Mars and its moons.
The spacecraft went silent less than two months after its launch when a faulty command sent from Earth caused it to shut down.
In a separate study, Loeb and his colleagues found that the object’s brightness, rapid rotation and orbital characteristics were consistent with those of the missing spacecraft.
They suggested that sunlight exerting pressure on the spacecraft’s metallic body and solar panels could explain its unusual movements.
The object is expected to pass within 32 million miles of Earth in 2028 and approximately 10 million miles in 2039.
However, scientists may not have to wait that long to establish its true identity.
Japan’s Hayabusa2 spacecraft is scheduled to rendezvous with the mysterious object in July 2031.
Loeb has predicted that the Japanese spacecraft’s cameras could end up finding a Soviet-made machine rather than a space rock.
His theory, however, remains unproven.
