I Why Do Stars and Hot Metal Show Different Colors at Similar Temperatures?

[bruha]

Hello I am interested about correlation between star surface temperature and its visioned colour ,for example orange red Arctur has surf temperature cca 4300 K ..but comparing to for example hot piece of metal? its temperature 2000 K respond white colour. ? What is a matter of this disagreemet?
Thank you very much. best regards T.Bruha

 

[davenn]

hi there
welcome to PF

Hello I am interested about correlation between star surface temperature and its visioned colour

you have labelled you thread with the intermediate tag indicating a higher education
what research have you done so far to answer this question ?

ohhh btw ... this should have been in the astronomy forum ... I will ask for it to be movedDave

 

[sophiecentaur]

There is a wide range of surface temperatures that produce a light that can be called "white" and the difference between them can often only be spotted when they are compared side by side. This wiki link shows how the Colour of a hot object relates to its temperature. The picture is only illustrative, of course but shows how Arctur (at 4300K) looks orange, relative to a hotter star at say, 6000K. See Planck's Law. The spectral curves for a black body will peak at different wavelengths, depending on the temperature (Google Colour Temperature) A very hot piece of metal can look white, when it's only a bit hotter than 'Red Hot'; that's a subjective thing.

 

[bruha]

Thank you very much for answer ,I will check links.
Best regards T.Bruh

 

[Vanadium 50]

Visible (perceived) color depends on intensity as well as frequency, so you won't be able to put temperature and color in 1:1 correspondence.

 

[bruha]

Hello thanks for answer
(I though something as this. I was hyphothesised if there could not be redshift effect but probably not...) hi T.Bruha

 

[sophiecentaur]

if there could not be redshift effect

I have a feeling that you are referring to appearance with the unaided eye(?).
Red shift is very slight and undetectable by the eye for sources that are actually visible unaided. I think that sources which display significant red shift would be too faint to see with optical viewing, even with a large telescope) and astrophotography would be needed to detect them - and measure the red shift.

 

[stefan r]

Hello I am interested about correlation between star surface temperature and its visioned colour ,for example orange red Arctur has surf temperature cca 4300 K ..but comparing to for example hot piece of metal? its temperature 2000 K respond white colour. ? What is a matter of this disagreemet?
Thank you very much. best regards T.Bruha

Molten iron:

Optical image of the star Arcturus:

Speaking of "white hot iron" and "red giant stars" makes sense when you compare them with similar objects. For instance a red hot iron and a blue star like Rigel:

..

 

[bruha]

Thank you very much for answer. so I understandt, that it is relative ,probably depends, on perceived intesity of radiation ( and therefore distance as well ).
Can I have still one question concerning gravitational redshift unit-beacouse in lot of articel I find as used unit m/s: so it is correct that redshift (%)= redshift (m/s)/300*10exp4? - derivating from light seconde distance?
thank you and best regards, Tomas Bruha

 

[stefan r]

Thank you very much for answer. so I understandt, that it is relative ,probably depends, on perceived intesity of radiation ( and therefore distance as well ).
Can I have still one question concerning gravitational redshift unit-beacouse in lot of articel I find as used unit m/s: so it is correct that redshift (%)= redshift (m/s)/300*10exp4? - derivating from light seconde distance?
thank you and best regards, Tomas Bruha

Can you link the article?
For a doppler redshift
z = v/c
v is the velocity, c is speed of light 3.00 x 10⁸m/s. z is (observed-emitted)/emitted wavelength. 100z is "percent redshift".

... - derivating from light seconde distance?...

Most astronomy measurements of gravitational redshift will be from much more than 1 light second. We measure from Earth and stars are many light years away. Am I miss reading that?

 

[bruha]

Hi this is just for fun…(this period is in Prag only observable planet Mars

Have nice time