I am working on fictional stars, and I want to have as many points about them as I can, and most things I found relatively easy, except for rotational speed.

I am not sure exactly how to find at what speed a star should be rotating in relation to its mass and spectral class. I found a small list of a few ones on wikipedia, but it doesn't help that much as it doesn't include the exact class I am looking for at the moment.

So, how is it that one can estimate what rotational velocity a star should have given the parameters. The parametres I know include Mass, Stellar Class, Radius, Density, Volume, Luminosity, Expected Maximum Age, Current Age (technically it changes as my world takes place over a long period, but the difference is in like, thousands of years, not billions) and Temperature.

I am aware massive outliers can exist, like Achernar, but I just need help finding like, the average, expected range so that I can use believable values.

Your help is much appreciated. Equations and citations would be beneficial, which is why I used the Hard Science tag.


As requested by Neil Iyer, here is a random one of my stars so you can try answering that. I still do request a generalized answer, though.

  • Class: F2.2V

    Mass: 1.35

    Radius: 1.187

    Density: 0.808

    Luminosity: 3.322

    Temperature: 7158 K

    Age: 3.6 Gyr

Mass, Radius, Density, and Luminosity are based on the Sun.

Edit 2:

One more specification, I am looking for equatorial velocity.

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    $\begingroup$ I mean, my question is moreso about finding generalized formulae concerning the subject, for me to use the equations myself. Not just an exact answer for one situation. Which would just lead to me needing to make hundreds of seperate questions. While doing a generalized formula or set of formulae could help me do it for all of my stars. But I guess I would put a random one of them up there. $\endgroup$ Oct 12 at 22:43
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    $\begingroup$ @NeilIyer OP isn't asking for "quantitative data", they're asking after a model of stellar physics. Adding extraneous details distracts from the focus of the Q imo. $\endgroup$
    – BMF
    Oct 12 at 23:09
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    $\begingroup$ @BMF Oh, I did not realize. Thank you for clarifying. $\endgroup$
    – Neil Iyer
    Oct 12 at 23:41
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    $\begingroup$ A second problem is that stellar rotation varies by latitude as well as depth. We can ignore depth for the purposes of your question, but it would help if you edit your post to indicate (I hope) that you're only interested in the equatorial velocity. (I found it interesting that the velocity slows down as you get closer to the poles.) $\endgroup$
    – JBH
    Oct 13 at 15:50
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    $\begingroup$ OK, I think I found the solution, but it's discussing math I haven't used since college 35 years ago and I couldn't hope to process any of it without dusting off a textbook. It's here and it's messy. It should be messy, because stars don't have a single angular velocity. That PDF goes into a lot more than just rotation, so it's a valuable resource, but may heaven smile on you as you start turning the arithmetic crank. I'm voting again for finding a similar star.... $\endgroup$
    – JBH
    Oct 13 at 16:03


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