There was no reason to fret, but perhaps reason to be wowed: "Florence," an asteroid stretching an estimated 2.7 miles wide, became the largest known asteroid to come as close as it did to our planet when it whizzed by Friday at 8:06am EDT.  

But though it came relatively close to Earth by space standards, it was still 4.4 million miles away, or about 18 Earth-Moon distances, according to NASA. Astronomers who've mapped Florence's orbit were well aware the asteroid posed no danger to Earth—and it won't get any closer to us until after 2500—and were thrilled at the prospect of its flyby, which provided an opportunity to study the mass up close. Radar images could perhaps reveal details of Florence's surface as small as 10 feet wide, per

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