
Rosetta witnesses birth of bow shock around comet - based2
https://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_witnesses_birth_of_baby_bow_shock_around_comet
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pocketstar
“As the supersonic solar wind flows past objects in its path, such as planets
or smaller bodies...”

>essentially anything moving with any velocity is supersonic in space

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semi-extrinsic
Not really. Attempt at explanation:

Solar wind is a stream of charged particles such as electrons and protons
which are emitted by the sun. Together these particles form a "weak"
(technical term "tenuous") plasma.

Plasma, as a state of matter, has quite a few resemblences to a gas. In
particular, the plasma has a thermal pressure and a density, and the
derivative of pressure wrt. density gives you a well-defined speed of sound
_for the plasma_. There is a type of waves in the plasma called ion-acoustic
waves, which propagate with this sound speed. (There are other types of plasma
waves with other speeds of sound.)

When a uniform flow of plasma is travelling faster than the plasma speed of
sound, nothing happens by itself. But when this flow hits an object, a bow
shock is formed, just as we see in front of the nose of a supersonic jet or a
speeding bullet.

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dotancohen
This is a very good, concise explanation for what usually takes three chapters
to explain. Bookmarked for the kids, thank you!

