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Author Topic: Fluorescence  (Read 248 times)

tkulogo

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Fluorescence
« on: November 30, 2017, 06:39:18 AM »
Would fluorescence have a significant impact on the appearance of a body lit by a very high temperature black body such as a 50,000K+ star?

Physics_Hacker

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Re: Fluorescence
« Reply #1 on: November 30, 2017, 11:18:45 AM »
It might if the body was made of such materials that would produce florescent effects. There are rocks that are naturally fluorescent but I'm not sure how much of an entire planet they could compose or cover enough to really have an effect on such a planet orbiting such a star but if you bring your black light poster I'm sure with the right star it would work...if you want the worst case of full-body cancer physically possible. .-. (And I don't even mean just skin cancer. A star producing that much ultraviolet would probably produce a ton of X rays too and probably a lethal dose of gamma rays, so...good luck lasting long close enough  for your poster to glow XD Oh and thats all assuming a star like that is even possible, but a "violet star" would have an extremely short lifespan I can tell you that...) A florescent planet might be possible under specific conditions though. I can do extra research if needed.

tkulogo

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Re: Fluorescence
« Reply #2 on: November 30, 2017, 12:06:51 PM »
I have a system with a star that just hit its white dwarf stage a few thousand years ago. It has a very plausible temperature of 154,000K. The black body calculations I made suggest that even a million-degree star wouldnít emit anything significant above soft X-rays (which are stopped by an earthlike atmosphere). Planets around a hot white dwarf could be terraformed and be usable for thousands of years. I have no way to estimate the magnitude of fluorescence effect. The output of a star like that would be almost all in the ultraviolet with the peak in the extreme ultraviolet range. Only about 1% of the energy output would be visible light, but the ultraviolet energy would still warm the planets. Would it be like a world under a black light, or would the atmosphere filter out enough ultraviolet to leave the visible blue light as the most unusual effect? I get that the light would be very piercing and harmful to the naked eye almost immediately, but Iím sure someone would want to live there.

Physics_Hacker

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Re: Fluorescence
« Reply #3 on: November 30, 2017, 09:09:19 PM »
Ah, a white dwarf; that makes a little more sense.
As for the effects, I'm afraid a planet with an Earthlike atmosphere and magnetosphere may be ale to protect from Gamma and X rays as well as a good portion higher frequency ultraviolet but lower frequency ultraviolet is a different story. A star outputtig that much light in ultraviolet form might have the effect of a giant black light but I suspect that even if it did, the survivability of that might be a problem. Now, if you're just looking for the visual aspect, sure, its possible that with the right soil/rock compositions on the surface it could have a fluorescent effect, (though ultraviolet certainly seems to be picky what it wants to make fluoresce... I keep a black light on in my room a lot, so I'd know about that odd little fact) but it might be best not to plan out a tourist attraction there unless you want there to be a lot of cancer involved, as Ultraviolet A passes through the atmosphere completely and Ultraviolet B is partially blocked, so although the very most dangerous is blocked by the atmosphere, less dangerous types could still be very harmful in large doses like this...Talk about a sunburn  :o I'm sure someone might want to live there but I don't think they'd stay long honestly, for one reason or another .-.
Also something of note, as I hope you're aware, white dwarves are extremely dim, so for planets to be heated by one enough to remain habitable I'm sure it would have to be really close...maybe closer than a planet could have formed...
I'm sure there's other things to mention about this scenario but at the moment I can't think of any more.

tkulogo

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Re: Fluorescence
« Reply #4 on: December 01, 2017, 06:42:30 AM »
Protection from the Blue Sun is mandatory, but I assume if you can terraform a world, you can deal with sunburn and eye protection. Worse case, theyíll live like space vampires. As for orbital distance from the white dwarf, it canít be close because the red giant phase wouldíve destroyed those planets. Interestingly enough, white dwarfs are very bright at first. Right at the end of fusion, our sunís bolometric luminosity will be hundreds of times what it is now, even though it will be around the size of the earth.

If someone wanted planets around an older white dwarf, white dwarfs have been found with disks of material around them that could theoretically form planets, even very close to the star because of the lack of stellar wind. The system would need to include a 2nd white dwarf to have donated material during its red giant phase.

Physics_Hacker

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Re: Fluorescence
« Reply #5 on: December 04, 2017, 10:32:51 AM »
Well, eye protection sure, but sunburn is a matter of atmospheric ozone and magnetic field... And yes, that's what my point was: The planet would have to be very close, but they couldn't be as lose as needed due to the red giant phase having obliterated any such planets. I'm not sure it would be that bright, sounds more like the nova itself or maybe the end-result red giant, but okay given that measure there might be planets that are habitable...for a little while at least. The habitable zone would migrate inward though, so to remain habitable a planet would also need to migrate inward. This could be done with an asteroid but it seems like eventually you'd have to get so close to the white dwarf (once it gets to a more "normal" age) that tidal forces might be a problem...

Having planets form out of what is essentially accretion disk material seems very doubtful, especially in such a window that such a planet could be habitable too. Accretion disks contain some of the hottest matter in the universe; imagine how long it would take for a planet made of that material to cool off! Plus, I suspect there would be too much Hydrogen and Helium involved to make a rocky planet without a thick H-He envelope... Not to say having much a planet is impossible, just extremely unlikely unless made by artificial means, but I mean, if you can build a planet these other problems are probably nothing to you, like a bug you can ust swat to get rid of and never see again.