this post was submitted on 15 Sep 2023
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Unprecedented Webb image shows newborn star's outflow moving at supersonic speeds (www.cbsnews.com)
submitted 1 year ago by ZeroCool@feddit.ch to c/space@beehaw.org
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[–] walden@sub.wetshaving.social 5 points 1 year ago (3 children)

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.

[–] Toast@lemmy.film 9 points 1 year ago (1 children)

Kerry Breen is a news editor and reporter for CBS News. Her reporting focuses on current events, breaking news and substance use.

[–] throws_lemy@lemmy.nz 4 points 1 year ago* (last edited 1 year ago) (1 children)

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

[–] walden@sub.wetshaving.social 2 points 1 year ago* (last edited 1 year ago)

I noticed NASA used it too, which is why I didn't shrug it off as bad reporting.

[–] Spzi@lemm.ee 2 points 1 year ago (1 children)

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/

[–] walden@sub.wetshaving.social 2 points 1 year ago

Interesting, thanks for digging into it!