What makes some meteor showers stronger than others?
It depends on how much dust a comet left in its trail and how close Earth passes to the thickest part. Fresh trails can make spectacular displays.
Some meteor showers give lots of shooting stars every year, while others are weak. And sometimes a usually weak shower suddenly puts on an amazing show. Why?
How much dust. Each shower comes from a comet or asteroid that left a trail of dust. Big, active comets leave more dust, making stronger showers. The Perseids and Geminids come from bodies that have left plenty of dust.
How close Earth passes. Earth might pass right through the middle of a dust trail, where the dust is thickest, or just brush its edge. Passing through the thick middle gives many more meteors.
Fresh trails. Each time a comet passes the Sun, it sheds a new trail of dust. Fresh trails are narrow and packed with dust. If Earth crosses a fresh trail, there can be a sudden burst of meteors, called an outburst, or even a meteor storm with thousands of meteors in an hour. The Leonids did this in 1833, 1966 and around 1999 to 2002.
Old trails. Over time, dust trails spread out, and the planets' gravity tugs them around. Some showers fade over centuries, while new ones appear.
Predicting. Scientists use computers to model where dust trails are and can sometimes predict outbursts years in advance. So if an outburst is predicted, it is worth staying up to watch!