Earthgrazer
A long, slow meteor that skims almost horizontally through the upper atmosphere, often seen when a shower's radiant is near the horizon.
When a shower's radiant has only just risen, its meteoroids arrive almost parallel to the ground. Instead of plunging steeply, they travel a long path through the thin upper air and may cross a large part of the sky. These are earthgrazers. They tend to look slow and long, sometimes lasting several seconds, and some are colourful.
They are rare because the radiant is low for only a short while, but they repay early observation. Evening Perseid sessions in August sometimes catch spectacular ones, and Geminid earthgrazers are possible in early December evenings. They also show how much an entry angle affects what we see: the meteoroid's speed is the same, but a shallow path spreads the light over a much longer track.
An extreme example is the Great Daylight Fireball of 10 August 1972. A body a few metres across passed over the western United States and Canada, dipping to roughly 57 kilometres above the ground, before skipping back out into space. It left no meteorites. To spot earthgrazers, watch low in the sky in the direction of the radiant soon after it rises, preferably from a site with a clear, flat horizon.
Related terms
Level: Enthusiast Teens and adults