bus that didn’t stop

At www.space.com/31419-asteroid-2015-yb-earth-flyby.html … a bus sized asteroid buzzed past the Earth on the morning of December 19th – almost unannounced. It didn't stop. In fact it was not sighted until 2 days prior as it was a dark object. The scary bit is that it came within 36,800 miles of our planet, well within the orbit of the moon. Satellites fly above the surface at 22,000 miles high and the moon orbits at 239,000 miles away – so this was a relatively close flyby. Apparently there are millions of asteroids and defunct comet parts orbiting the Sun in the neighbourhood of the Earth. Only 13,500 Near Earth Objects have been catalogued – to date. These are invariably the big boys – the little chappies are elusive.