[Earth has a new 'minimoon', scientists announce]

[Earth has a new 'minimoon', scientists announce]

The first known asteroid to orbit Earth, asteroid 2006 RH120, was discovered using the Catalina Sky Survey in September 2006.

The new moon is thought to be between 1.9 and 3.5 metres across.

You read that right: no link to artificial objects has been found meaning this is likely a straggler space rock hurtling through the solar system, and not a gift from aliens or smugglers in space.

Kacper Wierzchos and Teddy Pruyne of the Caltalina Sky Survey shared images of the object they discovered on Halloween past year from a telescope atop Mt Bigelow in southern Arizona.

The asteroid, known as 2020 CD3, is only the second asteroid known to orbit Earth. Often, these objects simply slide across our planet and quickly return to space, but occasionally they approach the correct angle to enter an orbit. So, when they encounter Earth's gravity, the planet gives them a little tug, so that they fall into orbit around us.

"Orbit integrations indicate that this object is temporarily bound to the Earth", the researchers explained in an announcement. But astronomers are racing against the gravitational tug-of-war between Earth and our traditional moon. The asteroid is small, and even higher estimates suggest that the rock is not more than about 3.5 meters in diameter. But scientists say Earth likely has another moon-at least for now-that's no bigger than a vehicle, New Scientist reports.

Scientists at Catalina Sky Survey told The New York Times that the 2020 CD3 was also expected to be just another asteroid orbiting near the Earth.

These are known as "quasi-satellites" of the Earth. For instance, 2016 HO3 was discovered a few years ago trailing behind Earth about 13.6 times farther than the Moon. It was then observed repeatedly in the days that followed, allowing astronomers to learn more about the object.

In the end, whatever happens to our little visiting moon, it's good to know that we can spot things in space as small as a washing machine. "Horseshoe" asteroids circle the sun, but Earth's gravity shoos them away from our planet and forces them into odd U-shaped orbits. Now, astronomers working out of the University of Arizona's Steward Observatory think they may have discovered a second natural satellite - or at least a temporary one.

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