When meteoroids flash through the Earth's atmosphere, they bore tunnels through the air, leaving behind narrow meteor tracks that are heated by the collision of the fast-moving incoming object with atoms of highly diluted atmospheric gases. Most meteoroids are bits of space debris the size of a grain of sand. The width of the tracks they make has long been known to be narrower than a meter, but until recently, more precise measurements have been impossible to make.

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More info: Subaru telescope web page