Here’s what we know about the second “ minimoon ” detected on Earth

Spotted earlier this year, asteroid 2020 CD3 is just the second temporary natural satellite, or minimoon, to ever be 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.

Asteroid 2020 CD3 was first spottedre by Catalina Sky Survey astronomers from the University of Arizona on February 15th 2020. Some preliminary calculations have been made on its size and orbit, but new research published in the Astronomical Journal provides the most definitive analysis to date of this rare minimoon.

In fact, “rare” might not be the right way to put it. More like “rarely detected”. Minimoons, or temporary natural satellites, are probably quite common – they’re just notoriously hard to see, due to their small size and inconstant character. But as the Institute of Astronomy (IfA) at the University of Hawaii points out in a declaration, about 1 in 1,000 meteors that burn in Earth’s atmosphere once per minimoon. These objects are not large enough to cause problems on the Earth’s surface, and they tend to make a few wacky loops around the Earth before resuming their walk around a more persuasive object, the sun.

Minimoons may seem trivial, but 2020 CD3 has attracted a lot of attention; the new article has 23 authors from 14 different academic institutions.

First, the new document ruled out the lingering possibility that CD3 2020 was a comeback piece of space junk. The surface / mass of the object and its low brightness suggest that it is an asteroid silicate and not, for example, a rocket propellant abandoned or roadster Tesla capricious. The same cannot be said of a prospective minimoon 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 1.2 meters wide, so it’s a bit bigger than a dishwasher and certainly bigger than a breadbox. Authors say it’s probably a fragment that broke off from a larger asteroid and that it originated somewhere between Mars and Jupiter.

“It’s amazing that modern astronomical telescopes can detect minibons the size of large boulders as far away as the moon,” astronomer and IfA study co-author Robert Jedicke said in the University of Hawaii declaration.

The researchers were also able to characterize the object’s orbit more precisely. In fact, the 2020 CD3 has been in minimoon mode for 2.5 years – we just didn’t know that. The object had turned Earth since 2018, but it has embarked on a close-up approach, during which time it was detected by scientists at 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 stay attracted the study the authors by surprise, because the simulations predicted a shorter duration for the object. However, the findings were “consistent with simulated minimoons that lunar close encounters, providing additional support for the orbital models,” as researchers to write. Furthermore, the object is spinning faster than the speed predicted by theoretical models, suggesting that “our understanding of meter-scale asteroids needs to be revised.”

Indeed, it looks like we still have a lot to learn about these things, which makes sense, given that this is only the second known minimoon, the first being 2006 RH120, detected 14 years ago. The minimoons now represent good targets for future missions, as underlined Grigory Fedorets, astrophysicist at Queen’s University Belfast and lead author of the new article.

“Minimoons effectively bring the asteroid belt closer to Earth so that, in astronomical terms, we can reach and touch them, and potentially collect samples,” he said.

A mission to a minimoon (has a nice ring) could provide unique insight into the early conditions of our solar system, while also providing a nearby platform to test asteroid mining techniques, according to Fedorets.

We can’t be sure if CD3 2020 will ever revisit these parts, but as the authors of the new article point out, we should expect to find minimoons in the years to come, especially with the next one. Vera C. Rubin Observatory.