2
$\begingroup$

So, a while back I have stumbled across some articles about "pink black holes" and just put it off as a scam, like many news. But not so long ago I found Paul Francis, an astrophysics researcher, and his very colourful vest was what actually intringued me on what character he might be.

After some research, I saw that he has worked on those "pink black holes". I'll leave you here the link to the page he wrote: https://astronomy.swin.edu.au/sao/guest/francis/

So I won't go into the details, (I dare to assume everything needed for an introduction is up on the link), but I was actually curious if anyone had any news about the pinkish colour of quasars?

I saw in another context that the colour pink is a conciliation between blue and red that our brain literally "makes up" since between blue and red should be green, but our eyes do not detect any green whatsoever (pink does not appear in a rainbow either, it has to be a colour touching red AND blue at the same time). But that's really all I know.

So, many quasars are pink. We don't know why. But we are still trying to find out!

He does say that we have no idea what makes those quasars actually pink, and from what I understood, no particles makes these blue and red lights at the same time possible. But the thing is that this research is from 2000, but I can't seem to find any more interesting information.

Finally, I would like to ask the community:

Do we have any news on what our cherished pink quasars have become?

Improve this question
$\endgroup$
6
  • $\begingroup$ I can only guess... It seems that quasar is non-thermal radiation source, i.e. it does not follow black-body radiation law, and so for some reason it mostly produces red photons, others being approximately at $80\%$ in quantity compared to red and so pink is the resulting color. $\endgroup$
    – Agnius Vasiliauskas
    Commented Jul 26 at 22:32
  • 1
    $\begingroup$ Anais-Ellie Gucek wrote: "between blue and red should be green" - on the color wheel pink is also between blue and red, even closer than green, and if you add colors with blue and red photons that also gives pink. green is its own base color, we have RGB for red green blue from which all colors mix $\endgroup$
    – Yukterez
    Commented Jul 27 at 2:06
  • $\begingroup$ @Yukterez What’s the “color wheel” in physics terms? $\endgroup$
    – safesphere
    Commented Jul 27 at 4:31
  • $\begingroup$ @safesphere You can think of the color wheel as a representation of the angle around the white point on the chromaticity diagram, which itself is a slice of the gamut of a chosen color space, and the color space (e.g. LMS color space) is what can be defined in physical terms, namely via the sensitivity curves of the different kinds of photoreceptors. $\endgroup$
    – Ruslan
    Commented Jul 27 at 9:14
  • $\begingroup$ @Ruslan Thanks for your explanation. Let me summarize: color wheel => angle around the white point => chromaticity diagram => slice of the gamut => chosen color space => sensitivity curves => different kinds of photoreceptors => physics. This is overly convoluted involving numerous steps of made up concepts and is inaccessible to non-specialists. My question is in terms of: color wheel => physics. For example, on the diagram in Simon’s link above, everything, but the pink in the upper left corner is simply the rainbow of the spectrum (the wavelength of the visible range), except for the pink. $\endgroup$
    – safesphere
    Commented Jul 27 at 21:48

1 Answer 1

Reset to default
2
$\begingroup$

What makes black holes pink ?

First, we need to clarify some terminology. The article you linked to does not say that black holes are pink. It says that the light emitted by some quasars might appear pink in the visible spectrum. A quasar is an active galactic nucleus that is powered by a supermassive black hole. But most black holes are not quasars.

I don't see any mystery here. The article you is simply saying that rather than emitting visible light entirely at the blue end of the spectrum, as most astronomers had assumed, some quasars emit light across the whole range of the visible spectrum. If you measure the intensities of the light at specific wavelengths using filters, then you can replicate these data points with a colour of "pinkish-purple" (it's not clear whether this is for one specific quasar or an average across all the quasars that Francis observed). I assume the observed spectra were corrected for red-shift, although I don't think that is specifically stated in the article.

Francis does not hypothesise a mechanism that would give rise to the specific observed mix of visible wavelengths. Wikipedia says

Red quasars are quasars with optical colors that are redder than normal quasars, thought to be the result of moderate levels of dust extinction within the quasar host galaxy. Infrared surveys have demonstrated that red quasars make up a substantial fraction of the total quasar population.

You might get more information if you ask at Astronomy Stack Exchange.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.