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Can someone explain the use of "supersonic" in relation to space? I'm used to it meaning faster than the speed of sound, which in our atmosphere varies greatly and slows at high altitudes because of the lower temperature.
this post was submitted on 15 Sep 2023
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Lol
I mean, NASA use 'supersonic' in this report
The team measured the velocities of the innermost outflow structures to be roughly 48-60 miles per second (80 to 100 kilometers per second). However, the difference in velocity between these sections of the outflow and the leading material they’re colliding with — the shock wave — is much smaller.
https://webbtelescope.org/contents/news-releases/2023/news-2023-141
I noticed NASA used it too, which is why I didn't shrug it off as bad reporting.
Can someone explain the use of “supersonic” in relation to space?
Great question! Made me search for answers. Although this answer does not have any sources, it seems to stand well on it's own:
Supersonic has a well-defined meaning. It means a speed that exceeds the local speed of propagation of pressure waves. In cold gasses, Mach 1 (the speed of sound) is rather low. In hot gasses, it is higher.
We don't talk about sound in space, because the density of gasses is too low to support any significant energy transfer to solid objects like eardrums. Nevertheless, "sound" waves (i.e. pressure waves) do travel through any gaseous medium. Therefore, the local speed of "sound" is well-defined.
By 'kathyastro': https://www.cloudynights.com/topic/815726-does-supersonic-have-any-meaning-in-space-nasa-press-release/
Interesting, thanks for digging into it!
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An otherworldly image captured by the powerful James Webb Space Telescope shows the outflows surrounding a fast-moving newborn star that will someday grow into a cosmic body like the sun.
The image shows the star and the Herbig-Haro objects surrounding it.
Herbig-Haro objects are "luminous regions" that appear around newborn stars and are formed when stellar winds or jets of gas form shock waves that collide with nearby gas and dust particles at high speed, NASA said in a news release Thursday.
The photo is "roughly 5 to 10 times higher spatial resolution" than any previous image of the star and the objects, NASA said.
However, the shocks are moving "relatively slow in comparison to more evolved" types of the same star.
Molecules within the star and outflows emit infrared light, which Webb can use to map a structure.
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