Temporal Distortion from Randy Halverson on Vimeo.
The night sky as viewed in central South Dakota and near Madison, Wisconsin in 2011. At 0:53 and 2:17 in the video one can see a "meteor with a persistent train," explained at the Bad Astronomy column at Discover:
Technically, that’s called a persistent train, and it’s not actually smoke. As a meteoroid (the actual solid chunk of material) blasts through the air, it ionizes the gases, stripping electrons from their parent atoms. As the electrons slowly recombine with the atoms, they emit light — this is how neon signs glow, as well as giant star-forming nebulae in space. The upper-level winds blowing that high (upwards of 100 km/60 miles) create the twisting, fantastic shapes in the train.And this interesting side note:
I’ll note it’s not really friction that causes a meteor to burn up. Most of the heating is due to the meteoroid’s hypersonic passage through air, which compresses the gas, heating it up violently. The heat melts the rock (or metal) in the meteoroid, which then blows off, leaving behind a train that fades rapidly. But the glow from the ionized gas takes much longer to decay, leaving the persistent train.The only excuse NOT to watch this full-screen is if you don't know where the button is.
What an absolutely gorgeous video!ReplyDelete
I have a lot of respect for Dr. Phil Plait, but I think the discussion about friction vs compression of gas is a distinction without a difference.ReplyDelete
Gas is compressed because a very fast solid thing (meteor) is pushing them out of the way as it travels through space. The compression causes heat.
Friction occurs because on substance (meteor) is coming into contact with another substance (gas) and they are pushing on one another rapidly causing heat.
They are both just slightly reworded ways to say that the metallic atoms on the surface of the meteor are having many very rapid electroweak interactions with the particles (nitrogen, oxygen, etc) in the air.