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Illumination ?

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#1 StarHugger

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Posted 16 June 2020 - 05:03 PM

After reading the following on the Astronomical Leagues webpage "Everything that you see in the night sky is visible to you because of light from a star. The stars themselves, nebulae, planets, moons, are visible because of starlight. Even dark nebulae are visible because they block the illumination of stars or other objects lit up by stars. We exist because early generations of stars generated the elements that make up our planet and the chemical elements required for life. It is not an understatement to say that we exist because stars exist" I am confused as ionized gas itself glows like in fermi bubbles being ionized by the gamma rays of an active galactic nucleus but this in tern is caused by a black hole wich was once a star so I guess the quote is then correct even after the stars physical structure has altered and it is no longer a star. So am I Right and in turn the Astronomical League is also right or are there other physics that can illuminate or illuminate what is seen astronomically in visible or other wavelengths of light? Curious I am. Thanks in advance for any input anyone might contribute.
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#2 Arcamigo

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Posted 16 June 2020 - 05:22 PM

Well, the cosmic background is radiating in microwaves and that is glowing from a time before stars existed.


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#3 robin_astro

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Posted 17 June 2020 - 04:01 AM

The CMB does not count as that is not (now) at visible wavelengths.

 

The supermassive black hole in an AGN however is a good potential candidate for visible light production from a source unrelated to stars. (The heated accreting material produces light at visible wavelengths directly, particularly H alpha.)  The question then remains whether these can form in the absence of stars. ie the are they formed from primordial Hydrogen or from coalescing stars ? 

 

Brown dwarfs are not strictly stars as they are not massive enough to initiate thermonuclear fusion but some would be hot enough to glow dull red  from the energy generated from the  contraction under gravity.  

 

The light from lava flows on planets from geological activity must make some small contribution as must our own generated light pollution but one could argue that these could not exist in the absence of stars.

 

Any others ?

 

Robin


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#4 robin_astro

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Posted 17 June 2020 - 04:24 AM

The CMB does not count as that is not (now) at visible wavelengths.

 

 

Actually, thinking about it a bit more, if the energy distribution of the CMB is a true Planck curve there should still be a vanishingly small fraction of photons at visible wavelengths even though the temperature is now only 2.7K 

 

Robin


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#5 Arcamigo

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Posted 17 June 2020 - 10:59 AM

The CMB does not count as that is not (now) at visible wavelengths.

 

The OP said "can illuminate or illuminate what is seen astronomically in visible or other wavelengths of light"

 

Viewing in visible light is only possible in our region of the universe. The farther away you want to see, the more red shifted light is. That's why the James Webb Space Telescope is replacing Hubble. The CMB was glowing in photons, except those photons are now shifted so far towards the red end of the spectrum that we are seeing it as microwaves.


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#6 robin_astro

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Posted 17 June 2020 - 02:40 PM

 

 

Viewing in visible light is only possible in our region of the universe. 

The CMB is a blackbody spectrum not a single wavelength.  Although it peaks in the microwave region, it actually includes photons with a wide range of wavelengths, though as I said the number photons at visible wavelengths will be vanishingly small.

 

It depends what you mean by local. Light from very distant objects is certainly observable in the visible spectrum. For example here I am measuring in the visible spectrum light from an object 12 billion light years away (light travel time). The light was originally in the far UV but has been redshifted into the visible spectrum.

 

http://www.threehill.../spectra_22.htm

 

Cheers

Robin


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#7 robin_astro

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Posted 17 June 2020 - 02:49 PM

For example here I am measuring in the visible spectrum light from an object 12 billion light years away (light travel time). 

 

http://www.threehill.../spectra_22.htm

 

and since it originates from material accreting onto a supermassive black hole it also potentially counts as "non stellar" light.

 

Robin


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#8 Arcamigo

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Posted 17 June 2020 - 03:26 PM

and since it originates from material accreting onto a supermassive black hole it also potentially counts as "non stellar" light.

 

Robin

I completely agree with you Robin. You have a lot of interesting material on your website that I look forward to reviewing. Thank you for sharing. One could argue, perhaps pedantically, that since a black hole was originally a star, an accretion disk it creates, and all radiation emanating from it, is an indirect result of stellar action, even if it wasn't from fusion.



#9 gregj888

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Posted 17 June 2020 - 03:35 PM

Do we know for sure SBHs originated from stars or went through a stellar phase?



#10 robin_astro

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Posted 17 June 2020 - 05:17 PM

Do we know for sure SBHs originated from stars or went through a stellar phase?

A good question. I am not clear what the current consensus is on this which is why I said

 

"The question then remains whether these can form in the absence of stars. ie the are they formed from primordial Hydrogen or from coalescing stars ?" 

 

 (A quick look at Wikipedia throws up several  hypotheses ranging between the collapse  of star clusters,  large gas clouds coalescing to  form "quasi stars" which then collapse into massive black holes, and the merging of hypothetical primordial black holes formed during the big bang)

 

Robin



#11 StarHugger

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Posted 18 June 2020 - 01:16 AM

Interesting so far, there are also the population three stars wich are said to have populated the early universe gone now because they wouldent survive the current physics the population two and one stars can, those very early stars must have existed to create the supernova wich gave rise to population two stars theoretically. Not much known about those stars though and hopefully that changes at some point with some deeper seeing...


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