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PostPosted: Sun May 21, 2017 10:07 pm 
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Agemegos wrote:
Traveller wrote:
When the star collapses into the black hole, it would start taking in all the matter it could find, including planets.

It'll only take in planets etc. if there is some mechanism that removes their orbital energy and angular momentum. And that's no more likely for planets orbiting a black hole than for planets orbiting a star.

*falls on my sword*...you're right. Apparently what I thought is a common misconception, as there have been computer simulations posted which refute this misconception. That said, wouldn't the amount of radiation generated by the collapse and subsequent creation of the black hole sterilize absolutely everything within range, leaving planetary masses potentially orbiting a black hole, but burned out and totally dead?

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PostPosted: Sun May 21, 2017 10:52 pm 
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Baron Opal wrote:
Agemegos wrote:
Feasible? Or likely?

Well, informally they're the same thing. "Feasible" does sound better to the ear since I'm crafting the system, however.


Not to me. "Feasible" means "able to be done"; feasibility is a property of plans, projects, proposals, solutions. The distinction with "possible" is different from that of "likely" or "plausible", and is worth preserving.

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Baron Opal wrote:
The inhabitants look up in the sky at the Sol Adligatus, farm their black and purple flora

This black and purple flora is chemosynthetic, I suppose, as it grows in complete darkness.


Photosynthetic. I was imagining that there would be plenty of UV from the black hole from infalling matter. (Where did the accretion disk come from? I don't know. That's a step further down that I've gotten, yet.) The thylakoids in the chloroplasts would appear black if they absorbed those particular wavelengths.


Okay, I guess. It doesn't sound plausible to me, but I could well be wrong.

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These inhabitants — how did they survive being inside a supernova? Or did they evolve later on an airless, waterless moon?

Thus hiding the planet / moon behind the jovian. Also accepting that a good portion of the atmo- and hydrospheres would be eliminated. But, only one city of 10,000 would need to survive. (c.f. Toba) I'm also picturing that the planet needs to survive a blast wave and not a prolonged baking, which may be incorrect.


Supernovas typically last for weeks or months, the occultation of jovians' moons only for hours.

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It may be that I'll need to have the black hole be wandering and captured by the system. Which will have unfortunate consequences for the original star.

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Last edited by Agemegos on Sun May 21, 2017 11:14 pm, edited 1 time in total.

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PostPosted: Sun May 21, 2017 11:03 pm 
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Traveller wrote:
Agemegos wrote:
Traveller wrote:
When the star collapses into the black hole, it would start taking in all the matter it could find, including planets.

It'll only take in planets etc. if there is some mechanism that removes their orbital energy and angular momentum. And that's no more likely for planets orbiting a black hole than for planets orbiting a star.

*falls on my sword*...you're right. Apparently what I thought is a common misconception, as there have been computer simulations posted which refute this misconception.


There is a relativistic phenomenon, an innermost stable circular orbit within which orbiting objects lose energy somehow — gravitational wave formation, perhaps — and slowly spiral inwards, but it is very, very close to the black hole, far too close for the orbit of a pre-supernoval planet of the original star.

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That said, wouldn't the amount of radiation generated by the collapse and subsequent creation of the black hole sterilize absolutely everything within range, leaving planetary masses potentially orbiting a black hole, but burned out and totally dead?


I think so. My feeling is that a supernova would not just strip any possible jovian planet of its gaseous mantle, but evaporate the chthonian remnant, and any moons. (The "solar wind" from a supernova goes at 10% of lightspeed! And it expells many solar masses of the stuff in only days or so. And the star brightens by a factor of hundreds of thousands, raising black-body temperatures in its vicinity by a factor of up to a thousand!) But I don't actually know enough astrophysics to say, and have neither done nor seen any calculations.

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PostPosted: Mon May 22, 2017 1:16 am 
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Agemegos wrote:
Baron Opal wrote:
Photosynthetic. I was imagining that there would be plenty of UV from the black hole from infalling matter. (Where did the accretion disk come from? I don't know. That's a step further down that I've gotten, yet.) The thylakoids in the chloroplasts would appear black if they absorbed those particular wavelengths.


Okay, I guess. It doesn't sound plausible to me, but I could well be wrong.

Check out the "Purple Earth hypothesis", although that's only relevant in that there could have been a different type of compound to absorb light that has since been out-competed. As long as the cellulose and cell membranes can be transparent to UV, and repair themselves quickly enough, it would work. Now that I think about it, the plants might be black and red-orange.

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Supernovas typically last for weeks or months, the occultation of jovians' moons only for hours.

Ah, an important point of which I was ignorant. Drat.

Right-o! Captured wanderer or super-science stellar collapser it is!


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PostPosted: Mon May 22, 2017 3:04 am 
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Baron Opal wrote:
Check out the "Purple Earth hypothesis", although that's only relevant in that there could have been a different type of compound to absorb light that has since been out-competed. As long as the cellulose and cell membranes can be transparent to UV, and repair themselves quickly enough, it would work.

I am skeptical. With UVA, maybe. But UVB has enough energy per photon to destroy not-particularly-delicate molecules.
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Now that I think about it, the plants might be black and red-orange.

Image

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PostPosted: Mon May 22, 2017 3:42 am 
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Agemegos wrote:
Baron Opal wrote:
Check out the "Purple Earth hypothesis", although that's only relevant in that there could have been a different type of compound to absorb light that has since been out-competed. As long as the cellulose and cell membranes can be transparent to UV, and repair themselves quickly enough, it would work.

I am skeptical. With UVA, maybe. But UVB has enough energy per photon to destroy not-particularly-delicate molecules.
Quote:
Now that I think about it, the plants might be black and red-orange.

Image


Yes, much like that, except the leaves rather than the flowers or produce. (I think the magenta is red clover, based on what I am driving by these days.) Anthrocyanins (may) and UV absorbants like benzophenone (do) absorb UVB and release the energy as heat. All you need is sufficient aromaticity.

I'm not going for hard science, here. But I do thank you for your help.


Last edited by Baron Opal on Mon May 22, 2017 5:59 pm, edited 2 times in total.

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PostPosted: Mon May 22, 2017 1:13 pm 
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Baron Opal wrote:
It may be that I'll need to have the black hole be wandering and captured by the system. Which will have unfortunate consequences for the original star.

Note that astrodynamic captures usually require the ejection of something with comparable momentum, in keeping with the conservation of momentum. Given that the lower limit on stellar mass black holes appears to ~2 Msun and main sequence stars this size (e.g., Sirius) have lifetimes less than a billion years, you're probably better off if the black hole is part of a binary and swaps its companion for the system primary, dragging the planets along.


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PostPosted: Mon May 22, 2017 6:13 pm 
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Good to know. Thank you!


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PostPosted: Tue May 23, 2017 1:56 am 
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Baron Opal wrote:
Agemegos wrote:
Baron Opal wrote:
Now that I think about it, the plants might be black and red-orange.

Image


Yes, much like that, except the leaves rather than the flowers or produce. (I think the magenta is red clover, based on what I am driving by these days.)

Those are salt ponds, and the colours are photosynthesising halobacteria — ones that use retinal and rhodopsin rather than chlorophyl. Let those rather than cyanobacteria become endosymbiotes or evolve multicellular forms and you would have just such orange and magenta leaves.

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My SFRPG setting, Flat Black

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PostPosted: Tue May 23, 2017 1:42 pm 
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Possibly relevant:

Neutron Star Planets: Atmospheric processes and habitability


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