Thanks for the question about IC 1613. It will help to keep the Very Mad Galaxy Man on his toes.......
Ron, a
supergiant blue or red star
will be as bright as visual magnitude 17, at the commonly adopted distance of IC 1613
I can do the maths if you want.....just a simple application of the equation linking absolute magnitude, apparent magnitude, and distance.
Incidentally, this galaxy may well have the most accurately known distance of any galaxy in the sky (
extremely large numbers of measurements have been made, using relatively accurate methods), so it is very easy to figure out how bright a -7 absolute Visual magnitude supergiant star will be at the distance of IC 1613
But the question that we have to ask is:
Is there a rich population of these supergiant stars in IC 1613, or are the brightest stars in this galaxy mainly Red Giants (which are much fainter than supergiants) ?
It has taken me an hour and a half of sweat and toil, but I have finally found some measurements of the visual and I-band magnitudes of 15000 stars in a large area of IC 1613
From these magnitude measurements, I can say with some certainty that:
- At V-band ("visual") 17th magnitude there are only a few stars in this galaxy.
- In the V magnitude range 18 to 20 (though mainly between magnitude 19 and 20), there are enough stars in this galaxy to give the impression of a moderately-dense scattering of stars
- the majority of the stars in this galaxy start in the range V = 20 to 21 magnitude. (the bright red giants are about 21st magnitude). From this magnitude and fainter, this galaxy is very populous.
Best Regards,
Robert Lang
So it would seem that IC 1613
does have a modest population of very luminous young OB stars;
certainly, there are enough of these "bright little stellar beauties" in IC1613, to look like a nice frosting of bright stars over the underlying "galactic cake" of the innumerable very faint stars in this galaxy.
Here is a color-magnitude diagram of IC 1613, with V minus I (star color) on the horizontal axis and I-band magnitude of the stars on the vertical axis :
Looking at the situation more subjectively, I would say that most images of IC 1613 (e.g. first generation digitized Sky Survey) do show a substantial dusting of resolved stars, which must be very luminous stars, given the arguments I have made above.
I would like to discuss the relationship between the stellar resolution in photos of IC 1613 and M31 and the SMC, as per your question, but I am very sorry to say that for now I am out of time!