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Luminosity of supergiant stars

Posted: 10 Nov 2018 00:51
by An'shur
I am not sure where would it be appropriate to post it, so here it goes.

I have version 0.980E.

So the thing is, that luminosity of procedural supergiants does not correlate with this graph.

Image

In other words, I think that luminosity/absolute magnitude of supergiants and hypergiants is too low in SE.

I've been searching for supergiant stars (luminosity class above Ib) in globular clusters, and found out, that absolute magnitude of Ib, Iab, Ia and 0 stars lingers around -3.7 and rarely gets above -4.

► Show Spoiler


O and B main sequence stars however, follow the HR diagram well. So I wonder whether the super/hypergiant luminosity deficit is done on purpose or not.

Edit: Luminosity of supergiants outside of globular clusters seem fine.

Luminosity of supergiant stars

Posted: 11 Nov 2018 14:15
by FastFourierTransform
I probably don't get the actual issue you are seeing here but for me this is completely normal.

Absolute magnitude of a star is the apparent magnitude as seen at 32,6 light years from that star (10 parsec). In all your examples the stars are way closer to the observer so many of absolute magnitude -5 can look as bright as a -8 magnitude (remember -8 is brighter than -5 in the magnitude scale since it is inverted; brighter stars have lower positive values or larger negative ones as in this case).

Also remember that Yellow supergiants (as can be seen in the HR diagram) are in general dimmer than other supergiants.

Were you talking about this?

Luminosity of supergiant stars

Posted: 12 Nov 2018 11:24
by An'shur
I know that the magnitude scale is inverted, smaller the number, the brighter the object.

When I throw these examples of luminosity (4475, 3549, 2409) from my screenshots into this calculator it gives me these magnitudes: -4.39, -4.135, -3.715. None of these are yellow supergiants, the least luminous example (2409 LSol) is actually an O1.1 hypergiant. I checked again in SE and confirm that these types of stars in globular clusters are too dim, they fall to Ib class at best.

Image
This is one of the more believable catches from Messier 2 cluster. It should be 2 magnitudes brighter to be an Ia though.

But I think this star, which is not part of any globular cluster, is fine. (Like all these other dots around, supergiants and hypergiants)
Image

Luminosity of supergiant stars

Posted: 12 Mar 2019 21:36
by silikone
Speaking of supergiants, why is WOH G64 the brighest star by far? Approaching the LMC, I expected a certain Wolf-Rayet star to present itself above others instead.

Luminosity of supergiant stars

Posted: 13 Mar 2019 05:33
by HarbingerDawn
silikone wrote:
Source of the post Speaking of supergiants, why is WOH G64 the brighest star by far? Approaching the LMC, I expected a certain Wolf-Rayet star to present itself above others instead.

It could just be a catalog error. If you find erroneous information for catalog objects, please post about exactly which errors you found in the relevant sticky thread in the mods and addons forum so it can more easily be fixed.

Luminosity of supergiant stars

Posted: 13 Mar 2019 13:11
by A-L-E-X
silikone wrote:
Speaking of supergiants, why is WOH G64 the brighest star by far? Approaching the LMC, I expected a certain Wolf-Rayet star to present itself above others instead.

Maybe SE is picking up on something and we'll learn that those stars in the LMC have been overestimated.  I've long been suspicious of so many of the brightest stars we've ever located all being in one cluster (Tarantula), perhaps what we thought of as one star is actually multiple stars too close together for us to be able to separate them.  That mistake has been made before.

Also, Wolf Rayet stars should not be the most luminous stars, they dont have enough surface area- that should belong to hypergiant stars like S Doradus and Rho Cassiopeiae.