On November 8, 2020, our planet captured a tiny object — the Centaur upper stage rocket booster that helped lift NASA’s Surveyor 2 spacecraft toward the Moon in 1966 — from its orbit around the Sun and will keep it as a temporary moon for about four months before it escapes back to a solar orbit.
This photo shows a Centaur upper-stage rocket before being mated to an Atlas booster in 1966. Image credit: NASA.
The Surveyor 2 lunar lander was launched toward the Moon on September 20, 1966, on an Atlas-Centaur rocket.
The mission was designed to reconnoiter the lunar surface ahead of the Apollo missions that led to the first crewed lunar landing in 1969.
Shortly after lift-off, Surveyor 2 separated from its Centaur upper-stage booster as intended. But control of the spacecraft was lost a day later when one of its thrusters failed to ignite, throwing it into a spin.
The spacecraft crashed into the Moon just southeast of Copernicus crater on September 23, 1966. The Centaur upper-stage rocket, meanwhile, sailed past the Moon and disappeared into an unknown orbit about the Sun.
In September 2020, the object — first thought to be an asteroid and given the asteroid name 2020 SO — was spotted by astronomers from the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory using the NASA-funded Pan-STARRS1 survey telescope.
But the researchers saw the orbit of 2020 SO and suspected it was not a normal asteroid.
Most asteroids’ orbits are more elongated and tilted relative to Earth’s orbit. But the object’s orbit around the Sun was very similar to that of Earth.
It was at about the same distance, nearly circular, and in an orbital plane that almost exactly matched that of our planet — highly unusual for a natural asteroid.
As the scientists made additional observations of 2020 SO, the data also started to reveal the degree to which the Sun’s radiation was changing its trajectory — an indication that it may not be an asteroid after all.
“Solar radiation pressure is a non-gravitational force that is caused by light photons emitted by the Sun hitting a natural or artificial object,” said Dr. Davide Farnocchia, a navigation engineer at NASA’s Jet Propulsion Laboratory.
“The resulting acceleration on the object depends on the so-called area-to-mass ratio, which is greater for small and light, low-density objects.”
On November 8, the Centaur rocket booster slowly drifted into Earth’s sphere of gravitational dominance, a region called the Hill sphere that extends roughly 1.5 million km (930,000 miles) from our planet.
That’s where 2020 SO will remain for about four months before it escapes back into a new orbit around the Sun in March 2021.
Before it leaves, the object will make two large loops around Earth, with its closest approach on December 1, 2020.
_____
This article is based on a press-release provided by the National Aeronautics and Space Administration.
