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| Space on Dec 12, 2014

How high up are meteors when they begin to glow?

Meteors begin to glow almost as soon as they hit Earth’s atmosphere, but tend to vaporize (burn up completely) at varying altitudes.

December 13-14 peak night for Geminid meteors

Meteors are usually dust particles left behind by comets – bits of debris that enter Earth’s atmosphere from space. At what altitude do these meteors – sometimes called “shooting stars” or “falling stars” – become incandescent and begin to glow? That can vary.

Geminid meteor. Photo by Tommy Eliassen. Capture time: 00:12am, Dec 11, 2014.  Location: Lovund, Nordland, Norway.

Geminid meteor. Photo by Tommy Eliassen. Capture time: 00:12am, Dec 11, 2014. Location: Lovund, Nordland, Norway.

Meteors become incandescent – or glow – almost as soon as they hit Earth’s atmosphere. Some meteors, such as the Perseids in August, burn up in the atmosphere at about 100 kilometers – or 60 miles – above Earth’s surface.

Other meteors, such as the Draconids in October, fall to 70 kilometers – or about 40 miles – before they heat up enough to glow and vaporize. The difference is that the Draconids are much slower meteors than the Perseids. So the height in the atmosphere at which a meteor begins to glow depends on its arrival speed.

Image credit: aresaubern

There are a dozen major meteor showers every year – and many more minor ones.
Here are some meteor arrival speeds:

Leonids: 71 kilometers per second
Perseids: 61 kilometers per second
Orionids: 67 kilometers per second
Lyrids: 48 kilometers per second
Geminids: 35 kilometers per second
Fall Taurids: 30 kilometers per second
Delta Leonids: 23 kilometers per second
Draconids: 23 kilometers per second

By the way, the length of a meteor’s path across the sky doesn’t depend entirely on the meteor’s arrival speeds. It depends mostly on the angle at which the particle of dust slices through the atmosphere. If the particle arrives at a low angle, it enters the atmosphere more gradually, heats up more slowly, and cuts a longer swath across the sky than if it barrels in at a steep angle.

The size, composition, and density of the dust particle probably also affect the length of the path – but scientists still aren’t sure exactly how.