Fireball that flew over Japan in 2017 was tiny piece of giant asteroid that might one day threaten Earth

In the early morning of April 28, 2017, a small fireball crept across the sky over Kyoto, Japan. And now, thanks to data collected by the SonotaCo meteor survey, researchers have determined that the fiery space rock was a shard of a much larger asteroid that might (far down the road) threaten Earth.