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Spotted earlier this year, asteroid 2020 CD3 is only the second temporary natural satellite, or minimaon, ever detected around Earth. It didn’t last very long, but we learned some interesting things about our temporary companion and why a mission to intercept similar objects is a good idea.
The 2020 CD3 asteroid was first identified by astronomers from the Catalina Sky Survey at the University of Arizona on February 15, 2020. Some preliminary calculations have been made about its size and orbit, but new research published in the Astronomical Journal is providing the most definitive analysis to date of this rare minimaon.
In fact, “rare” may not be the right way to put it. More like “rarely detected”. Minimal, or temporary natural satellites, are probably quite common: they are only notoriously difficult to see, due to their small size and fickle nature. But as the University of Hawaii’s Institute of Astronomy (IfA) points out in a statement, about 1 in 1,000 meteors burning in Earth’s atmosphere were once a minimaon. These objects are not large enough to cause problems on the Earth’s surface and tend to make some strange turns around the Earth before resuming their journey around a more persuasive object, the Sun.
Trajectory of CD3 2020 from January 2019 to May 2020 (Image: Javier Roa Vicens)
Minimoons might sound corny, but the 2020 CD3 has gotten a lot of attention; the new article boasts 23 authors from 14 different academic institutions.
First, the new document ruled out the lingering possibility that 2020’s CD3 was a returning piece of space junk. The object’s area-to-mass ratio and low brightness suggest that it is a silicate asteroid and not, for example, a discarded rocket or a rebellious Tesla roadster. The same cannot be said for a minimum potential detected last September, an object strongly believed to be a second-stage Centaur rocket launched by NASA in 1966.
Asteroid 2020 CD3 is slightly smaller than preliminary estimates. It’s about 3.9 feet (1.2 meters) wide, so it’s a little bigger than a dishwasher and definitely bigger than a bread bin. The authors say it is probably a fragment that broke away from a larger asteroid and originated somewhere between Mars and Jupiter.
“It’s amazing that modern astronomical telescopes can detect as small a size as large boulders to the moon,” said Robert Jedicke, an IfA astronomer and co-author of the study, in the University of Hawaii statement.
The researchers were also able to characterize the object’s orbit with greater precision. As it turns out, the 2020 CD3 has been in minimal mode for the past 2.5 years – we just didn’t know that. The object had been circling the Earth since 2018, but swooped in for a close approach, during which it was detected by scientists with the Catalina Sky Survey.
In total, 2020 CD3 spent 2.7 years as a temporarily bound natural satellite before resuming its journey around the Sun. This long period took the study authors by surprise, as simulations predicted a shorter lifespan for the object. . That said, the observations were “in agreement with simulated minimions having close lunar encounters, providing additional support for orbital models,” the researchers write. Furthermore, the object rotates faster than the speed predicted by theoretical models, suggesting that “our understanding of the one-meter scale asteroids needs revision.”
In fact, it looks like we still have a lot to learn about these things, which makes sense, as this is only the second least known, the first 2006 RH120, detected 14 years ago. The lows now represent good targets for future missions, as Grigori Fedorets, an astrophysicist at Queen’s University in Belfast and lead author of the new paper, pointed out in the statement.
“The lows effectively bring the asteroid belt close to Earth so that, in astronomical terms, we can reach and touch them and potentially collect samples,” he said.
A one-minimaon mission (it sounds nice) could provide unique insights into our solar system’s initial conditions, while also providing a nearby platform for testing asteroid mining techniques, according to Fedorets.
We can’t be sure whether 2020 CD3 will ever return to these parts, but as the authors of the new paper point out, we should expect to find lows in the coming years, especially with the upcoming Vera C. Rubin observatory.
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