[neilep (OP)]

Dearest Naked Science Peeps,



Are black holes the blackest things ever ? even blacker than the black paint stuff that is really black ?


I asked the sheep in 'Baa Baa Black Sheep' and all it did was donate wool to a Master, a Dame and a Boy !!..I mean, what kind of help is that ? absolutely rubbish !!!






Sagittarius A just moments ago.

















whajafink ?




Hugs et les shmishes




mwah mwah mwah


Neilxxxxxx





Baa Baa Black Sheep
Are Blackholes the blackest thing ever ?
I just donate wool
Which I think is very klevur !!

[Halc]

They're not perfectly black, but they're blacker than a place in space with no stars in it.

The black sheep don't quite win, but close.

[Bored chemist]

They're not perfectly black, but they're blacker than a place in space with no stars in it.

The black sheep don't quite win, but close.

Why is the one in the middle winking at us?

[evan_au]

Apparently, the current record-holder for blackest materials (as of 2019) is a forest of carbon nanotubes grown on aluminium, claimed to absorb 99.995% of incoming light.
- Ultrablack materials are very useful in construction of telescopes, as they reduce those annoying lines radiating from bright stars, and other optical defects.
See: https://sitn.hms.harvard.edu/flash/2019/back-black-new-blackest-material/

But black holes are far blacker: Despite the accretion disk of a black hole getting hot enough to emit X-Rays, the event horizon of a solar-mass black hole has an effective surface temperature of around 60 nanoKelvins, due to Hawking radiation.
See: https://en.wikipedia.org/wiki/Hawking_radiation#Overview

[neilep (OP)]

lol...Thank ewe Halcy

They're not perfectly black, but they're blacker than a place in space with no stars in it.



The black sheep don't quite win, but close.

[neilep (OP)]

Very interesting, thank ewe very much evan.
Can I ask further then, if that substance absorbs 99.995% of light, then where does the light go ? what happens to the absorbed light ?

Apparently, the current record-holder for blackest materials (as of 2019) is a forest of carbon nanotubes grown on aluminium, claimed to absorb 99.995% of incoming light.
- Ultrablack materials are very useful in construction of telescopes, as they reduce those annoying lines radiating from bright stars, and other optical defects.
See: https://sitn.hms.harvard.edu/flash/2019/back-black-new-blackest-material/

But black holes are far blacker: Despite the accretion disk of a black hole getting hot enough to emit X-Rays, the event horizon of a solar-mass black hole has an effective surface temperature of around 60 nanoKelvins, due to Hawking radiation.
See: https://en.wikipedia.org/wiki/Hawking_radiation#Overview

[Halc]

what happens to the absorbed light ?

It gets warm, and to prevent it from getting warm enough to radiate IR light back out (ruining their nice high percentage), it needs to be pulled away by other means, presumably by something on the other side keeping it cool.

The Webb telescope needs to be kept cooled to just a couple degrees Kelvin, and most of that is done by completely blocking light from Earth and sun, but that only works so far, and active cooling (heat pumps) must be used to get it fully to where they need it.

So don't put a woolly tongue on the telescope.  Baaaa-d idea.

[neilep (OP)]

Last time I licked a telescope it was January !!..that WAS a baaad idea 


So, the light is dispelled via heat after being absorbed. Like an exhaust !




Thank ewe Halc

what happens to the absorbed light ?

It gets warm, and to prevent it from getting warm enough to radiate IR light back out (ruining their nice high percentage), it needs to be pulled away by other means, presumably by something on the other side keeping it cool.

The Webb telescope needs to be kept cooled to just a couple degrees Kelvin, and most of that is done by completely blocking light from Earth and sun, but that only works so far, and active cooling (heat pumps) must be used to get it fully to where they need it.

So don't put a woolly tongue on the telescope.  Baaaa-d idea.

[munmin89]

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