Earth captures its second 'mini-moon' -- Asteroid 2020 CD3

Earth captures its second 'mini-moon' -- Asteroid 2020 CD3

Astronomers working at the Catalina Sky Survey, University of Arizona have discovered a possible mini-moon orbiting the Earth, now cataloged by the International Astronomical Union (IAU) as 2020 CD3.

2020 CD3 flew past Earth at a distance of just 0.12 LD / 0.00031 AU (46 375 km / 28 816 miles) on February 13, 2020. This is the 18th known asteroid to flyby Earth within 1 lunar distance since the start of the year and the second closest. 

According to the researchers, the 2020 CD3 appears to have been orbiting our planet since it was first captured by the Earth's gravity three years ago.

"It's a big deal as out of one million known asteroids, this is just the second asteroid known to orbit Earth," said Kacper Wierzchos, a researcher specialist for the Catalina Sky Survey who made the discovery along with fellow astronomer Theodore Pruyne.

Initial observations suggest that the mini-moon is very small, about the size of a car, with a diameter approximately 2 to 3.5 m (6 to 11 feet).

The Smithsonian Astrophysical Observatory's Minor Planet Center said 2020 CD3 will be our temporary moon. "No link to a known artificial object has been found," they wrote. "Orbit integrations indicate that this object is temporarily bound to the Earth."

Grigori Fedorets, a research fellow at Queen's University Belfast in Northern Ireland, stated that the Earth's new satellite is heading away from the planet and will eventually be gone in April.

These briefly-caught space rocks either move straight into the atmosphere where they burn upon entry or skim around before being ejected back to the solar system.

Only the smallest number of passing space objects can possibly be a mini-moon. According to a 2012 simulation including 10 million virtual asteroids, the Earth only captured 18 000 in its orbit, making such things hard to spot and super rare.

In 2019, a paper published in the Astronomical Journal also suggests that a temporary mini-moon may have entered the Earth's atmosphere and exploded as a fireball over Australia in 2016.

The only confirmed object that orbited the Earth was 2006 RH120, which took trips around the planet for about 10 months-- from September 2006 to June 2007.

By studying the minimoon's unusual looping orbit, astronomers and scientists can learn more about how the Earth captures these objects and how to improve observing them in the future.

Featured image credit: Catalina Sky Survey

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