# Tag Info

0

So I use the following logic: Define 'red', 'green' and 'blue' light in terms of the wavelength ranges those colours encompass (from here) Calculate the average spectral radiance across each wavelength range, for a defined temperature Define the RGB value to be the relative ratios of each colour's spectral radiance with 255 defined as the colour with the ...

8

Ok, here's my take on calculating the color of a blackbody, or any spectrum in fact: Disclaimer: I'm not a color theorist, and there may be more accurate methods. But the result, shown in the bottom, looks about right. Spectrum First note that since color is a function of the relative intensity in various wavelength bands, it doesn't matter whether we ...

2

Yes. Stars (those objects that are supported by hydrogen fusion) can be as cool as spectral type L2. Brown dwarfs can be as warm as M4/5 when they are young. i.e. there isn't a clear spectral type Vs mass relationship. It depends on age too.

4

According to Eric Mamajek's table of main sequence stars, the absolute V-magnitude of zero corresponds to late B-type stars. The values that bracket zero are B8V with $M_{\rm v} \approx -0.2$ and B9V with $M_{\rm v} \approx 0.7$. There is a fair amount of scatter around the main sequence so it is likely that some stars a few spectral subtypes away may have ...

5

A star with magnitude 0 would be 85 times brighter than the sun (since Magnitude=-2.5 log(Luminiosity)) Referring to the H-R diagram on Wikipedia shows that there is quite a range of spectral types possible with this luminosity: from B type main sequence stars, and A type sub-giants, such as 4 Sco There are also G and K and M type Giant stars with this ...

8

There isn't a one-to-one relationship between spectral type and absolute magnitude. Instead, there is a mean relationship with a fair bit of scatter around it. The reason is that the luminosity of a star of a given effective temperature depends on its composition/metallicity and how far along in its main sequence lifetime it is. Basically, late B-type main ...

1

The absolute magnitude quantify the luminosity of an object at a standard distance of $10\,pc$ from earth. For example, in the case you mentioned, Vega becomes dimmer then at its actual distance (about $7\,pc$) . To answer your question, I don't think there is an actual star with exactly 0 absolute magnitude. If there is then, following the formula of the ...

6

This is what Wikipedia says about it: When the MKK classification scheme was first described in 1943, the only subtypes of class O used were O5 to O9.5. The MKK scheme was extended to O9.7 in 1971 and O4 in 1978, and new classification schemes that add types O2, O3, and O3.5 have subsequently been introduced. It references the paper A New Spectral ...

1

I don't believe that O0 is a real classification(see this chart), but if it were following the temperature steps it would probably be around 80,000-90,000 degrees Kelvin. The hottest star we know of is WR 102, which is 210,000 degrees Kelvin, and that is much, much hotter than my predicted O0 temperature. So the short answer is yes, O0 temperature stars ...

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