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Earlier this year, highly sensitive telescopes on Earth discovered a dishwasher-sized asteroid that was temporarily circling the Earth-Moon system. In essence, the object, known as 2020 CD3, was a natural satellite, or minimaon, albeit only briefly. In a new study, researchers confirmed that 2020 CD3 is indeed a space rock rather than a man-made contraption, making it only the second least not detected so far.
Rarely detected by not rarely present
Not all asteroids whiz past the Earth, some may get trapped in our planet’s orbit before escaping into deep space. Astronomers say that by studying these temporary “minimaons”, it is possible to answer important mysteries surrounding asteroids. The challenge, however, is to monitor these small, fast-moving objects.
In 2006, astronomers found the first and, at the time, the only known natural satellite besides the moon. The temporarily captured orbiter (TCO) called 2006 RH120 measured only 2-3 meters in diameter and orbited the planet for 13 months before it freed itself from Earth’s gravity, only to be immediately taken back into orbit around the sun. This TCO is so small that NASA initially thought it was Apollo 12’s third stage Booster Saturn S-IVB. However, subsequent observations have established that it was, in fact, a captured asteroid.
Since then, there had been other candidates for the minimaon, but all of them turned out to be false positives, which on closer inspection turned out to be the Apollo-era rocket boosters or the Chinese Chang’e missions, but it’s not the case of 2020 CD3.
In a new study, an international team of 23 astronomers performed calculations on data from the Catalina Sky Survey, showing that the asteroid’s area-to-mass ratio and low brightness were indicative of a silicate object.
“Let’s compare the surface with the mass. For rocket thrusters, which are hollow, the surface to mass ratio is much higher, “said Grigori Fedorets, a researcher at Queen’s University in Belfast. Universe Today.
According to Fedorets, 2020’s CD3 is only 1-2 meters in diameter, which is expected to disintegrate in the planet’s atmosphere if it ever enters a collision course with Earth. It may never happen, though. When astronomers reversed the mini-asteroid’s path, they found that the object had been circling the Earth-Moon system since 2018. After 2.7 years as Earth’s natural satellite, the tiny object – believed to be a fragment of a much larger asteroid from the main asteroid belt between Mars and Jupiter – has resumed its journey around the sun.
“According to our simulations, an average minimaon would only be captured for about nine months … that’s a longer capture time than we expected,” Fedorets told Universe Today.
CD3 is only the second natural minima that astronomers have discovered so far. But, when you think about it, it is truly extraordinary that we have come this far with detection technology that we can now detect and track objects the size of a boulder up to two million kilometers from Earth. Of course, there are many other minima, or temporarily captured objects, currently orbiting the Earth. According to the astronomers, there should be “a steady state population with captured objects between 1 and 2 meters in diameter at any one time, with the number of captured meteoroids increasing exponentially for the smaller size.”
Other minima should be identified once the next Vera Rubin Observatory becomes operational in 2021. And since these objects are believed to be as old as the solar system itself, studying them could offer new insights into the evolution of the
The results were reported in Astronomical Journal.
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