The Earth has captured something interesting in its gravity that will orbit our planet for a few months before it escapes and ultimately ends up in a solar orbit. The object it has captured isn’t an asteroid. It’s believed to be the Centaur upper stage rocket booster that helped pushed Surveyor 2 toward the moon in 1966. The object was first detected by the Pan-STARRS1 survey telescope on Maui in September.
The telescope noticed that the object followed a slightly but distinctly curved path in the sky, which was a sign of its proximity to the earth. The observed curvature is due to the observer’s rotation around the Earth’s axis as the planet spins. Initially, the object was believed to be an asteroid orbiting the sun and was given a standard designation by the Minor Planet Center of 2020 SO.
Scientists at the Center for Near-Earth Object Studies at the NASA Jet Propulsion Laboratory looked at the object’s orbit and believed it wasn’t a typical asteroid. Typically, an asteroid’s orbit is more elongated and tilted relative to the orbit of the earth. However, the orbit of 2020 SO around the sun was very similar to that of the Earth at about the same distance, nearly circular, and in an orbital plane that was an almost exact match for our planet.
That was highly unusual for an asteroid. Further observations revealed that the sun’s radiation was changing the orbit of 2020 SO, which doesn’t happen with an asteroid. After analyzing over 170 detailed measurements of the object’s position over the last three months, the impact of solar radiation pressure became evident and confirmed the low-density nature of 2020 SO.
Researchers then set out to determine where the suspected rocket booster came from. Surveyor 2 was a lunar lander launched towards the moon on September 20, 1966, atop an Atlas-Centaur rocket. The mission’s goal was to investigate the lunar surface ahead of the Apollo mission that put humans on the moon in 1969. However, control of the Surveyor 2 spacecraft was lost shortly after it separated from the Centaur upper stage booster.
Ultimately the spacecraft crashed into the moon while the Centaur upper stage rocket flew past the moon and disappeared into an unknown orbit around the sun. Ultimately, 2020 SO is expected to remain in orbit around the Earth for about four months, with the closest approach expected on December 1 before it’s released to orbit the sun once more.