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Asteroid’s fly-by shows why it’s wise to keep our eyes on the skies

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But they will do so at a distance further from Earth than the Moon – more than 5 million kilometres – so there’s no risk of impact.

And it’s not like they have snuck up on us, either.

NASA noted the asteroids had been “well observed” since 2000 and 2010 respectively, but any celestial object that wanders within 1.3 astronomical units (the distance from our planet to the sun) is deemed a near-earth object, and astronomers keep an eye on them. Just in case.

Keeping track of near-earth objects, Professor Benedix said, was currently our best defence against a global calamity.

Professor Benedix is a cosmic mineralogist and astro-geologist, and specialises in tracing the formation of the planets and moons through the remnants of the early solar system – asteroids.

“There’s millions of rocks out there,” she said.

“We don’t see every single one of them, but I think we’re mostly on top of the things that could do some serious damage.

“We probably do get rocks passing by the Earth pretty often, and we get rocks passing in between the Earth-Moon distance reasonably so, but they’re all going to be relatively small overall.”

The reason we get so many small space rocks buzzing past our planet is because bigger asteroids crash into each other further out in the solar system, the collisions fragmenting them and creating many more rocks, which then often find their way inwards towards the Sun.

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“There’s a lot of very small material coming by the Earth all the time, but the big stuff is much more rare,” Professor Benedix said.

When asteroids enter our atmosphere, they’re then deemed meteors –bits of space rock that make it to the ground intact are meteorites.

The asteroid – or, potentially, comet – widely credited with wiping out the dinosaurs hundreds of millions of years ago was somewhere between 10 and 100 kilometres across, but even small meteors can have an impact.

Professor Benedix pointed to a prominent crater in Arizona about 1 kilometre across, which would have been caused by a meteor roughly 50 metres across.

The meteor which streaked across the Russian sky and captured in dramatic dashcam and CCTV footage in 2013 was likely about 20 metres.

But, aside from making sure we’re not about to follow same path as the previous dominant species on the planet, there’s a lot to be gleaned from studying asteroids and their orbits.

“Everything that we think might potentially hit us we continue to calculate the orbit because it can change based on how the objects in the solar system is moving around and those orbits can change over time,” Professor Benedix said.

“What might be on a potential collision course now might not be in another two years.”

This most recent passerby – like many others – likely has its origin in the asteroid belt found between Mars and Jupiter, sent inwards by the gravitational push-and-pull from the Sun and other planets.

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“All asteroids, they kind of are the babies of the solar system that never grew up,” Professor Benedix said.

“They give us a lot of information about what the very origin of the solar system was like, so we can get information about how old the solar system is, what it was potentially made of originally.

“Even back to the point where it wasn’t even planets yet, or even a star, just a big cloud of gas and dust.”

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