Meteor showers occur when the Earth passes through a field of cosmic debris. As that debris crosses into the Earth’s atmosphere, each piece burns up, sometimes creating the blazing streaks of light we call shooting stars. These chunks of rock or ice are gone for good, so it’s true that a meteor shower loses some of its material, or fuel, with every flurry.
But there are ways for a shower to be replenished, says David Meisel, executive director of the American Meteor Society. The Geminids, which appear every December, are fragments from an asteroid called 3200 Phaethon. When 3200 Phaethon swings past the sun, it heats up and pieces break off, littering its orbit with fuel for shooting stars. Given that the asteroid is about three miles in diameter, it will take a long, long time—”millions of years,” says Meisel—for all that material to be exhausted.
Even if the asteroid or comet behind a meteor shower were to break apart altogether, it would still take tens of thousands of years for the dust to disperse. A small portion would burn up in the Earth’s atmosphere, but most of the dust would collide with itself and spiral into the sun.
A meteor shower doesn’t have to run out of fuel to disappear. The outer planets can tug a comet out of its natural periodicity, such that its debris may lie in Earth’s orbital path on one pass and not at all on the next. “You can’t depend on a comet to produce a nice, steady stream all the time,” says Meisel. “If we understood it all, there would be no fun.”
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