Siphoning mass from stars

[Luzifer's right hand]

What side effects can you expect when you siphon huge ammounts of mass from a star? I'm thinking about at least 1x10^27 kg per year.

[Admiral Valdemar]

If you haemorrhage that from the core, then you're going to drastically alter it's reaction over time, leading to an early cycle alteration and possibly violent premature death.

[Darth Wong]

Extracting 1/2000 of our sun's mass every year would have an effect over a long timeframe, but if you did it for just a couple of years, I can't imagine it would make a huge difference.

[Admiral Valdemar]

Course, it changes depending on class of star. A brown dwarf would be affected a lot easier than a blue giant, but then given one's nearly dead anyway, it probably wouldn't do much. If you sucked out far more mass within a few months, you could seriously fuck up the system if the star's sequence is altered and made unstable, going into the critical iron fusion stage earlier.

[Luzifer's right hand]

Extracting 1/2000 of our sun's mass every year would have an effect over a long timeframe, but if you did it for just a couple of years, I can't imagine it would make a huge difference.

What would happen if you extract mass of a long timefrime?
Assume the mass is harvested from the outer layers of the stars first.
Could you extrat mass until the fusion raction of the star stops or would happen something drastic before??

[Admiral Valdemar]

If you extract mass from the corona and surface rather than the core, then it may take a very long time before anything happens, since the core is where the fuel and reactions are taking place with the pressure from them helping push the resulting matter outwards in various chaotic currents. You could probably take a lot of mass off before the stellar body started losing cohesion and falling to pieces.

This is, incidentally, two forms of planet killing weaponry used by the Inhibitors in Revelation Space. One involves spinning the star via massive particle accelerators in a ring around the star's equator, using flux from waveforms made in the accelerator workings to rotate the star and constrict then loosen its body in sequence causing it to vent chromospheric matter at the poles to be redirected by larger arrays and used at will.

The other way involves finding a string, forming it into the "8" shape theorised to form gravitons, then plucking it at a resonant frequency to the star's surface and using this deflection to burrow to the star's core and cause it to vent as a more focused beam. Use the same apparatus to direct said spurt at a target of choice.

[Ariphaos]

What would happen if you extract mass of a long timefrime?
Assume the mass is harvested from the outer layers of the stars first.
Could you extrat mass until the fusion raction of the star stops or would happen something drastic before??

Except for red dwarfs, stars often throw off a notable percentage (up to 10% or so) of their mass without significantly affecting their core reaction - actually growing hotter while doing so.

Of course, you're siphoning off half a Jupiter mass or so. If you do this to a borderline red dwarf star (just above the threshold), you can basically turn it into one and prevent it from evolving off the main sequence.

In a bit of a wild conjecture... Doing it for long enough, I imagine this is fast enough to create a situation where the reaction at the core lacks the pressure to sustain it, so it billows outward, then collapses again, perhaps becoming a variable star or a flare star.

[Kuroneko]

For a Sol-sized star, 1e27kg represents about 6-7% of its radius if taken from the outermost layers. The temperature shoots up rather quickly inward (roughly linear in that region, 5.2e6K * (R-r)/R), so this process will definitely make the star much brighter over the short term as the outer, cooler layers are removed.

Ordinarily, one would expect the stellar material to simply expand outwards to fill the missing volume, but removing this outer shell to, say, Mercury's orbital radius represents, neglecting self-gravity, about 2e38J of work, so that the average force would be about 3e27N. It's not known what kind of structure performs all this work, but if the force is transferred to the star itself and the siphoning is fairly uniform, the resulting ~5e8Pa is comparable to the pressure at r = 0.72R for the Sun, so that we can definitely expect the star to initially contract even more than simply removing the outer layers, at least until this is done for long enough to affect the nuclear reaction rate; by conservation of energy, the temperature will increase also increase more than otherwise.

[Braedley]

Didn't any of you see that SG1 episode? Of course the star will go nova, it's only a question of timing.



Okay, I'll leave now.

[Solauren]

Sg-1 also involved a wormhole connected to a Blackhole....

However, it does raise a point

Wouldn't removing alot of mass from the star's core decrease it's relative gravity and cause it to go nova? (lacking the gravity to keep it's outer shell in tact)

[SirNitram]

[nitpick]The SG-1 wormhole was connected to a black hole, meaning that the gravity increased, not decreased, and contracted the core into prematurely fusing iron.[/nitpick]

No, you don't get novas from less gravity.

[Ariphaos]

Wouldn't removing alot of mass from the star's core decrease it's relative gravity and cause it to go nova? (lacking the gravity to keep it's outer shell in tact)

If you removed enough to reduce the escape velocity of the star below the molecular velocity of a notable number of its particles, you would get something like a planetary nebula, which is sometimes mistakenly called a 'nova'.

However, I imagine the shock of the core re-collapsing on itself would be more dramatic.

[Admiral Valdemar]

Didn't any of you see that SG1 episode? Of course the star will go nova, it's only a question of timing.



Okay, I'll leave now.

Remember, a nova is NOT a supernova. One is simply the removal of stellar surface material by another body which ends with a bang, the other is a giant star using up its fuel and collapsing with a bit of a bigger bang (slight understatement).

A hypernova is even worse, but we've yet to see one.