WBH Class VI Mass and Diameter

[bartlebyfosco]

Hi All,

First time poster.

I am really enjoying the World Builders Handbook. I have one question I could not find a comment on in any previous posts. I notice the the Class VI stars' mass descends as the subclass increases from B0 to B5. And yet the diameter more than doubles when you go from B0 to B5. I expected the diameter to decrease like the mass. I checked for any errata but could not see it.

Any chance the table switched the diameters? Do VI stars really get bigger and lighter as you go from B0 to B5? For those of you extrapolating B6 to B9 - what values have you chosen for those subclasses for mass and diameter?

 

[Geir]

Hi All,

First time poster.

I am really enjoying the World Builders Handbook. I have one question I could not find a comment on in any previous posts. I notice the the Type VI stars' mass descends as the subclass increases from B0 to B5. And yet the diameter more than doubles when you go from B0 to B5. I expected the diameter to decrease like the mass. I checked for any errata but could not see it.

Any chance the table switched the diameters? Do VI stars really get bigger and lighter as you go from B0 to B5? For those of you extrapolating B6 to B9 - what values have you chosen for those subclasses for mass and diameter?

I have to admit that I can't find my references for this particular section, but the sdO and sdB subclasses - what's in there as the O and B VI stars are really rather odd ducks - stripped red giants with a mostly helium atmosphere or white dwarf mash-ups, whereas the other 'half' or cool subdwarfs of G-M are also rather old, but hotter than their mass would indicate because they're so poor of metals.

Since I can't find the source, I'm pretty sure what I did was extrapolate off a few data points for the O and B stars, but I believe it is as intended. And the luminosity formula does correspond to the diameters and temperatures listed, so it is at least consistently listed.

 

[bartlebyfosco]

Thank you so much for checking. If the answer is "these guys are all a bunch of weirdos" then that works for me.

 

[WHULorigan]

In general Type VI "Subdwarf" Main sequence stars are like Type V "Dwarf" Main sequence stars, but the Type VI stars usually formed during an earlier era in the universe when the total number of heavy-nuclei-forming supermovae and neutron star mergers was far fewer in total number, and there were thus fewer heavy elements present in star-forming nebulae. Lower metalicity in stellar material means it is less opaque and traps heat less well, leading to a smaller-size stellar atmosphere envelope for a given core size.

But most hot, high mass Type VI Main Sequence Sub-Dwarfs should have gone supernova long ago. So an O or B type Subdwarf is a more recent star that got small by some other mechanism. One of which is a giant star whose outer atmosphere got removed by some means, leaving behind only the exposed naked helium burning core, as Geir mentioned, known as a "Blue-Subdwarf" or Blue Dwarf.