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Mining some stars might be almost easy due to their extremely high rotational rates

(04-09-2021, 01:07 AM)selden Wrote: [ -> ]Mining some stars might be almost easy due to their extremely high rotational rates


Brown dwarfs’ high surface gravity kind of cancels the benefit, as you can see with their rather low oblateness. In general, bigger stars tend to rotate faster, and a lot of A and B type stars can rotate so fast they’re close to breaking up, which means those are actually good candidates for ‘easy’ starlifting, unlike these brown dwarfs. See Dschubba in OA.
For colonisation missions aimed at brown dwarf systems, we would hope that planet/moons would be present, because mining the dwarf itself would be challenging. Any atmosphere it had would be quite compact.
How difficult would mining a red giant be?  As it's pulsating, the material is expanding outward, so it already has momentum away from the core of the star.  Wouldn't that make it easier?

Astronomers tell us the temperature of a red giant is some number like 3000K.  But how much would difference in temperature would there actually be, between the core and the outer atmosphere?   How steep is the gradient between the atmospheric temperature and the temperature of particles in the interplanetary medium outside the star? 

Its low density would mean it takes longer to gather a quantity of materials, but given their technology and longevity, would the low density be much of a problem?  

Imagine something like a bishop ring existing near a red giant, so it periodically is engulfed by the outer atmosphere of the pulsating red giant, and the provolves inside the red giant have to prepare and adjust...
Red giants are loosely bound, and so are giant blue stars; they emit so much energy, though, that activity in proximity to such a star is very difficult. Not something to be attempted lightly.
By contrast there are any number of brown dwarfs - stellar objects in that not-quite-a-star-but-too-big-to-be-a-planet range - that have very rapid spins and upper-atmosphere temperatures that are relatively easy to design for. In their case it's essentially the same process as skimming fuel from gas giants. And the ones with the most rapid spins are pretty inexpensive in terms of delta-vee and energy input.

We used to think of 'fuel' in terms of hydrogen or methane to burn. In the OA context that would be pretty retro, but it's probably still worth skimming for deuterium fuel. Or if you just plain need a lot of matter for something and don't care much what you harvest, it doesn't matter.
It seems that there might be quite a few red giants with companion bodies in configurations which would aid in starlifting/mining operations. A quick search of EG articles on binary stars didn’t seem to locate mentions of this possibility, though.

See, for example, this recent paper “Binarity as the Origin of Long Secondary Periods of Red Giant Stars”

The proposed explanation is an orbiting stellar or sub-stellar body with a tail of dust and gas pulled from the red giant, as determined by a study of about 350 (out of 16000) candidates.

P.S. Unfortunately, the handful of stars referenced directly in the paper all seem to be in the LMC.