Earth Has Two 'Mini Moons' and We Just Had Closest-ever Encounter with the Second

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A mini-moon is an object orbiting a planet but isn't actually a moon. And in the latest discovery, a total of two mini-moons have been spotted around Earth.

The second mini-moon has been orbiting us for around 2.7 years and a lot has been discovered about the mysterious space object since then.

The object has been named as 2020 CD3 and recently it came really close to Earth. At 8,100 miles, it was at the closest it has ever been. The mini-moon's changing levels of brightness allowed astronomers to study its rotation-rate which was determined to be three minutes. The data was collected using the Lowell Discovery Telescope. However, it was earlier spotted by NASA-funded Catalina Sky Survey in February, as per reports.

The car-sized asteroid had been a subject of interest ever since its first appearance. Earlier observations determined it was a human-made object. Some astronomers hypothesised that it was the remnant of space shuttle launched decades ago.

Now, Large Monolithic Imager on the LDT was used to observe CD3's rotation. Based on the brightness and rotation observation it has been confirmed that it is an asteroid. Both NASA's centre for Near-Earth Objects and The minor-Planet centre have now categorised it as a near-earth asteroid.

"The rotation rate was probably the largest unanswered question of this research. The Lowell team showed that it rotates slower than anticipated for objects of this size range," said Grigori Fedorets from Queen's University Belfast.

The first "mini-moon" was observed in 2006. 2020 CD3 is the second. There was a third mini-moon assumed to grace our orbit named 2020 SO which was observed earlier this year by the Catalina Sky survey in September. The 26-feet long mysterious space object was travelling to earth at a speed of 1,500 mph.

However, closer inspection revealed that it wasn’t an asteroid at all. A former NASA director later revealed that it was Surveyor 2 lunar lander mission that had partially failed. Its parts have been floating in space since its launch in 1966.