THE MYSTERY OF THE NON-ASTEROID ASTEROID

 Asteroids occasionally come into close proximity with Earth as they orbit the Sun, sometimes even entering Earth's orbit for a brief period. One notable example is 2020 SO, which was captured in Earth's orbit on November 8, 2020, and remained there until February 2021. During this time, the object frequently approached Earth, coming as close as 55,000 km.

However, 2020 SO exhibited peculiar characteristics from the outset, distinguishing it from typical asteroids. Early observations revealed that its orbit was influenced by non-gravitational effects due to solar radiation pressure. This prompted astronomers to speculate that the object might be hollow and, therefore, not an asteroid.

Subsequent spectroscopic observations confirmed that 2020 SO was composed of stainless steel, indicating that it was, in fact, a fragment of a man-made rocket. The object's unique spectrum, altered by continuous exposure to cosmic and ultraviolet rays, allowed scientists to deduce that the rocket had been in space for an astonishing 54 years!

Further analysis revealed the size and shape of the object as an elongated body approximately ten meters long. Combining all available information, it was determined that 2020 SO was the upper stage of an Atlas-Centaur rocket, likely from the Surveyor 2 lunar mission launched in September 1966.

Credit: NASA