At a distance of around 8 billion kilometers (5 billion miles, or 54 AU -- a little beyond Pluto's orbit), an icy space rock silently hurtles toward the inner solar system steadily gaining speed.
This piece of space debris -- composed of primordial rock and ice -- measures no more than 26 kilometers (16 miles) in diameter, and as it plunges sunward, it will pass the orbits of Pluto, Neptune, Uranus, Saturn, Jupiter, Mars and even power through our neighborhood before being flung back into the depths of interplanetary space.
You'd think that's all we would see of Comet Swift-Tuttle until it returns in about 133 years time, but you couldn't be more wrong.
Every year we are reminded of its fleeting presence as the Earth intercepts the comet's orbit and sweeps up some of the fragments it left behind. Like a celestial vacuum cleaner, Earth collects everything in its path and treats us to one of the greatest shows the Universe has to offer: the Perseid meteor shower.
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