As early as September, the Pan-STARRS1 surveying telescope noticed an object following a slight but distinctly curved path in the sky, a tell-tale sign that it was being caught by Earth's gravity. Originally, this object was considered a near-Earth asteroid (NEA) and was given a standard designation by the Minor Planet Center (2020 SO). NASA JPL's Center for Near-Earth Object Studies (CNEOS), however, had a different theory.
Because of its orbit and the way the solar radiation seemed to keep it off course, NASA scientists have now concluded that the object might actually be the spent booster of the Centaur rocket that the Surveyor 2 spacecraft headed toward in 1966 Moon launched finding could have implications for future explorations that find mysterious objects near Earth (& # 39; Oumuamua occur).
The first clues were the highly unusual orbit of the object, which was about the same distance as the earth from the sun, in a similar orbital plane, and almost circular. The key clue, however, came when astronomers at Pan-STARRS and around the world made additional observations from 2020 SO, which showed the extent to which solar radiation was changing its trajectory.
Animation of the orbit of 2020 SO on November 8, 2020. The movement was accelerated millions of times faster than in real time. Photo credit: NASA / JPL-Caltech
Spent rocket stages are essentially empty tubes that, when disposed of in orbit, have a low density and a large surface area. As a result, solar radiation pressure pushes them around more than a high-density solid object (like an asteroid). Davide Farnocchia, NASA JPL Navigational Engineer who analyzed 2020 SO trajectory for CNEOS, stated:
“Solar radiation pressure is a non-gravitational force caused by light photons that are emitted by the sun and strike a natural or artificial object. The resulting acceleration of the object depends on what is known as the area-mass ratio, which is greater for small and light objects with a low density. "
In total, more than 170 detailed measurements of the position of 2020 SO were made in the last three months. This included observations made by the NASA-funded Catalina Sky Survey in Arizona and the European Space Agency (ESA) optical ground station in Spain. These showed how strong the pressure of solar radiation was, which confirmed the low density of 2020 SO.
The next step was to determine where the suspected rocket booster might have come from. To that end, CNEOS Director Paul Chodas ran the object's orbit in reverse, showing that 2020 SO had gotten relatively close to Earth a few times over the decades. However, analysis revealed that the object's closest approximation (late 1966) was close enough to Earth that it may have originated here.
This 1964 photo shows a Centaur upper stage rocket before it is paired with an Atlas booster. A similar centaur was used in the launch of Surveyor 2 two years later. Photo credit: NASA
This coincides with the launch of the lunar lander Surveyor 2, which was launched towards the moon on September 20, 1966 with an Atlas Centaur rocket. The mission was to explore the lunar surface before the Apollo missions to find possible landing sites. A day after it separated from its upper stage booster, one of the spacecraft's three engines failed to ignite and tossed the spacecraft into a spin.
The spaceship lost control and crashed into the moon southeast of Copernicus crater on September 23, 1966. Meanwhile, the spent Centaur upper stage rocket sailed past the moon and disappeared into an unknown orbit around the sun. As Chodas said, it is likely that it never escaped the gravity of the Earth-Moon system:
"One of the possible paths for 2020 SO brought the object very close to the Earth and the Moon in late September 1966. It was like a Eureka moment when a quick review of the launch dates for lunar missions showed a match with the Surveyor 2 mission."
The orbital path that 20202 SO has since brought back to Earth for a different approach. On November 8, 2020, it slowly drifted into the globe of the earth, a gravitational-influenced region that extends approximately 1.5 million km (930,000 miles) around the earth. It will stay here for another four months and will come next on December 1st. That way, astronomers can take a closer look at it and confirm its identity.
Artist's impression of the interstellar object "Oumuamua", which undergoes outgassing when it leaves our solar system. Photo credit: ESA / Hubble, NASA, ESO, M. Kornmesser
This discovery is also significant because it shows how low-density, large-surface objects can be accelerated by solar radiation pressure. The same principle shapes the design of solar sails and was even observed when the interstellar object “Oumuamua” left our solar system in 2017. Despite the lack of outgassing, the object accelerated through exposure to sunlight.
This behavior and unresolved questions about its form prompted Dr. Shmuel Bialy and Prof. Abraham Loeb, as is well known, to propose in 2018 that “Oumuamua could be of artificial origin. While Bialy is a postdoc at the Institute for Theory and Computation (ITC), Prof. Abraham Loeb is the Frank B. Baird Jr. Professor of Science at Harvard University and the founder of the ITC. As announced by Loeb Universe Today by email:
“The discovery of 2020 SO by Pan STARRS in September 2020 gives credibility to the idea that man-made objects can be distinguished from natural objects because they are pushed by sunlight. "Oumuamua was discovered by Pan STARRS in October 2017 and subsequent monitoring of its orbit revealed that just like 2020 SO, it was experiencing excessive pressure away from the Sun without showing a cometary tail."
“The fact that 2020 is SO a relic of our civilization reinforces the case that Oumuamua could be artificial, made by another civilization. The situation is similar to the activity I enjoy most while on vacation with my family, which is walking on the beach and looking at seashells. Every now and then we find a plastic bottle that is a relic of civilization. The newly discovered object 2020 SO is such a relic from our civilization. Perhaps Oumuamua is a relic from another civilization.
An artist's illustration of a light sail powered by a radio beam (red) generated on the surface of a planet. Photo credit: M. Weiss / CfA
In his upcoming book "Aliens", which will be available for purchase on January 26, 2021, Loeb deals with the special properties of "Oumuamua" and the possibility that it is a "message in a bottle" from an alien civilization.
By March 2021, 2020 SE will leave Earth orbit and assume a new orbit around the Sun. As NASA nears its long-awaited return to the moon, it's nice to be visited by an artifact from the early space age that recalls a time when humans first struggled to get to the moon.
Further reading: NASA