40 years ago, a comet came out of the blue in a surprise Earth flyby. Here's what we know now.

a blue-green comet in the night sky

Forty years ago this month, there came a show stopping celestial sight — literally a bolt out of the blue. 

A brand-new comet, that for several days made headlines around the world due to its exceptionally close passage near the Earth: A distance amounting to less than 3 million miles (4.8 million km), or about 12 times the distance of the Earth to the moon.