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Comment by est | Hacker News Reader

> WASP-127b, a giant gas planet located more than 500 light-years from Earth.

How do you define "sound speed" on a gas giant?

As a layperson I thought that was odd choice too and would be an Earth-centric measurement, but the paper on which this article is based references this paper: https://iopscience.iop.org/article/10.3847/1538-3881/ac51d2

Where they spell out a formula for the speed of sound in this type of planet given some assumptions. It's beyond my understanding, but I thought it was pretty cool. Section 4.4 if you want to have a look.

Then back to the article paper: https://www.aanda.org/articles/aa/full_html/2025/01/aa50438-...

> Using their formula we obtain sound speeds of the order of 3 km s−1 for WASP-127 b.

Very cool! Isn't it amazing what happens when you don't assume bad faith or incompetence on the part of the researchers? You have to like a paper that has a section discussing the precipitation of vaporized iron out of a planets atmosphere...mindblowing. Of course, that means doing a little homework to actually understand what they already know and avoiding the lazy "me and my preconceived notions and lack of domain knowledge are here to tell you why your wrong".

You can simulate the speed of sound based on atmospheric makeup and temperature. That said, 9 km/s is probably going to be supersonic in most media (for reference, the speed of sound in most metals is several km/s).

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