Why does Tabby's star dim?

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zuz

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I have heard one theory that Tabbys star dims is due to an alien megastructure. Where would they get the raw materials to build such a large object?
 

Drakkith

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Presumably from the astronomical bodies (planets, moons, asteroids, etc) within the star system or from other nearby star systems.
 

stefan r

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Hold up a sheet of aluminum foil. How much dimmer is your laptop screen?

You only need a few microns of material to block sunlight. In some cases a few nanometers.
Our solar system has iron based asteroids. The "low iron content" meteors that we find on Earth have more iron and nickle than anything else. If you take a cube that is 1 km on a side and roll it into sheets with one micron thickness then you have a surface that is 1 billion km2. More area than Earth.
Wikipedia says the inner belt in the solar system has over 750,000 asteroids larger than 1 kilometer. in order to block 20% of an F star's light you need more like 1012km2 That requires more like a 10 km scale asteroid. We know of around 10.000 of them in our inner belt.
 

DaveC426913

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We don't quite yet know what exactly is dimming Tabby's star.
It is likely some distribution of mass - likely dust or debris - around the star, the configuration of which still eludes us.

"Alien megastructure" - while scientists have entertained it as a possibility - is pretty much at the very bottom of the list.
 

zuz

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I doubt the alien theory also. But if you had the resources and energy to build such a structure, why would you need it?
 
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I doubt the alien theory also. But if you had the resources and energy to build such a structure, why would you need it?
It is worth reflecting carefully on the meaning of the word alien.
 
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I doubt the alien theory also. But if you had the resources and energy to build such a structure, why would you need it?
Ringworld ? Zoetrope ? Maybe they're trying to make a "blue midget" by reflecting all the star's radiation back at it. Perhaps Von Neumanns have been collating a heavy asteroid belt into nice neat piles around lagrangian points for the last 20,000 years.

:nb)
 

jim mcnamara

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This thread is off the rails a bit. Let's try General Discussion before we descend into total speculation. PF is not a good platform for making stuff up.
 

stefan r

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We should be able to make various models of dust engines. When a structure folds up it spirals down to the star. Once it gets hot it can unfold and blow out on the solar wind. Would be good for reaction mass.
 
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Ringworld ? Zoetrope ? Maybe they're trying to make a "blue midget" by reflecting all the star's radiation back at it.
I'm trying to run with this idea and figure out what purpose would making a "blue dwarf" have. Could it produce heavy elements without going supernova like a heavy star? Would it be a more efficient power source that your garder variety Dyson sphere?
 

stefan r

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This is way off topic. Not sure if continuing is physics forums appropriate. It is in the lounge so...:

Here is a paper on blue dwarfs. There are no blue dwarfs observed today. Accepted models suggest that there will be many natural blue dwarfs eventually.

Could it produce heavy elements without going supernova like a heavy star? ...
No, Blue dwarfs will only produce helium. Yes, blue dwarfs do not go supernova.

Tabby's star will never become a blue dwarf.

...Would it be a more efficient power source that your garder variety Dyson sphere?...
No. You are burning hydrogen either way. As a Shkadov thruster a blue dwarf would accelerate more than main sequence stars in the same spectral class.

It may be the least amount of mass needed to make a star that has both near solar luminosity and near solar temperature.

I'm trying to run with this idea and figure out what purpose would making a "blue dwarf" have.

Under what circumstances we are "making stars"? In your giant molecular cloud you have thousands of solar mass. You collapse your cloud as you process it. You need to fling mass away from the cloud in order for it to continue collapsing. Which mass you eject will depend on what product the customer wants delivered.

The blue dwarfs are most likely a byproduct. It is a way to dump large amounts of helium. You started with galaxy standard composition. The hydrogen went to someone, probably for energy. The metals became something else. There is a fair chance that collecting the metals was the motive for colonizing the cloud to begin with. Large amounts of helium is there and it is somewhat in the way. The manufactured blue dwarf has a purpose similar to the way piles of overburden have a purpose.
 
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Tabby's star will never become a blue dwarf.
I had to re-check what type of star Tabby's star is, because I was absolutely 100% convinced it was a red dwarf.
 

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