Comets orbiting the sun are very fragile. Bits and pieces break off and follow the comet in its orbit. When the Earth’s orbit intersects this trail of debris, some of the particles enter our atmosphere. They vaporize as they fall, creating streaks of light – a meteor shower.
A couple of decades ago, astronomers knew approximately when Earth encounters these streams of cometary debris each year. Now showers still aren’t totally predictable, but you do hear predictions for the best date, hour, and place on Earth to view a meteor shower.
The predictions are better than they used to be – due to improved telescopic observations of comets – and more accurate computer calculations. Astronomers now have better information about the trajectories of comets and their debris and about when Earth is closest to the debris trails.
A skywatcher still doesn’t know for sure how many meteors will be seen for any given event, but astronomers can calculate when the orbital paths of the Earth and comets’ debris will intersect – even for hundreds of years into the future.
Our thanks to:
Laboratory for Atmospheric and Space Physics
University of Colorado
Department of Space Studies
Southwest Research Institute