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Star Types in Universe

Nellkyn

SOC-11
I’ve been using my copy of Universe to transfer all the information I have on the Reaver’s Deep sector, mainly from the Cargonaut books.

As I’ve been entering the data for each star I’ve noticed a problem and I don’t know if it is due to a Universe bug or a mistake in the Reaver's Deep data. Two of the stars are listed as M0 IV but in Universe there is no M listing under IV. Can anyone let me know where the error is, in the software or the data?

Thanks in advance.

Nellkyn
 
Originally posted by Nellkyn:
As I’ve been entering the data for each star I’ve noticed a problem and I don’t know if it is due to a Universe bug or a mistake in the Reaver's Deep data. Two of the stars are listed as M0 IV but in Universe there is no M listing under IV. Can anyone let me know where the error is, in the software or the data?
There's no way in Traveller to generate an M IV (subgiant) star, and they don't appear to exist in reality either. It might be that they were supposed to be listed as M0 VI (subdwarf) stars perhaps?
 
Originally posted by Nellkyn:
As I’ve been entering the data for each star I’ve noticed a problem and I don’t know if it is due to a Universe bug or a mistake in the Reaver's Deep data. Two of the stars are listed as M0 IV but in Universe there is no M listing under IV. Can anyone let me know where the error is, in the software or the data?
There was a rule in CT Book 6 that said if you roll a K5-M9 subgiant (IV) or a B0-F4 subdwarf (VI) you should change the size to Main Sequence (V). Unfortuneately a lot of the data sets available seem to ignore this rule and so you get illegal stars. This becomes a problem in system generation as there are no luminosity figures to go on.

Universe tries (as much as possible) to be compliant with CT. So by design it will not allow illegal stars to be entered.

Regards PLST
 
Thanks very much for that Hemdian. I’ll have a look in Book 6 and make the changes to the Reaver’s Deep data.

Nellkyn
 
Originally posted by Malenfant:
There's no way in Traveller to generate an M IV (subgiant) star, and they don't appear to exist in reality either. It might be that they were supposed to be listed as M0 VI (subdwarf) stars perhaps?
Type IV subgiants are a brief trasitional stage between main sequence (type V) and giant (type III) stars. They're rare and don't stay in that state long.

Type VI sub-dwarfs are rare population II stars that occur in the galactic halo. They have low to no metals (anything other than H2 or He) and thus will not have planetary systems -- no rocks, no ice, just gas. Nothing to form a core for a gas giant, even. Neither type belongs in any serious attempt to model reality for gaming.
 
Originally posted by Tanuki:
Type IV subgiants are a brief trasitional stage between main sequence (type V) and giant (type III) stars. They're rare and don't stay in that state long.
Subgiants derived from the lowest mass stars than can get there within the lifespan of the universe can stay in that stage for about 900 million years. I don't think they're particularly ignorable - they're certainly less likely to be encountered though.

My point though was that M subgiants don't seem to exist. The reddest subgiants that can be found according to the stellar structure models that I have are around the mid-K end of the spectrum.

Type VI sub-dwarfs are rare population II stars that occur in the galactic halo. They have low to no metals (anything other than H2 or He) and thus will not have planetary systems -- no rocks, no ice, just gas. Nothing to form a core for a gas giant, even.
I think the jury is still very much out on that, actually. They have LESS metals, sure, but that doesn't mean that they have NO metals. Even a star with 1% of the metals that the sun has still has a fair amount of stuff that isn't H or He floating in the protoplanetary nebula around it. It might be more realistic to say that they'd have much smaller or fewer planets around them.

And you can get subdwarfs in the galactic disk too (IIRC, one of the nearest stars to us is a subdwarf), though they are much rarer than higher metallicity stars.

Neither type belongs in any serious attempt to model reality for gaming.
I disagree. They're rare, yes, but that doesn't make it unrealistic to model them in gaming.
 
I thought you could get Type IV subgiants in binary Type I Supernovae systems. No?

It only takes one Type II Supernova to dump a whole lot of metals into the surrounding gas clouds. Some massive stars would condense and go from T-Tauri to SN in tens of millions of years, dozens of times shorter than the accretion time for a star anywhere near Msol.

A true "first generation" star would be very hard to find. Maybe a smallish Type O could condense fast enough, yet live long enough to still be around today.
 
Originally posted by Straybow:
I thought you could get Type IV subgiants in binary Type I Supernovae systems. No?

It only takes one Type II Supernova to dump a whole lot of metals into the surrounding gas clouds. Some massive stars would condense and go from T-Tauri to SN in tens of millions of years, dozens of times shorter than the accretion time for a star anywhere near Msol.

A true "first generation" star would be very hard to find. Maybe a smallish Type O could condense fast enough, yet live long enough to still be around today.
So do you have values for the luminosity, mass, and radius of these 'missing' star types?

Regards PLST
 
Originally posted by Straybow:
I thought you could get Type IV subgiants in binary Type I Supernovae systems. No?
Not that I've ever heard of. Subgiants are stars that are in between the main sequence (V) and red giant (III) phases.


It only takes one Type II Supernova to dump a whole lot of metals into the surrounding gas clouds. Some massive stars would condense and go from T-Tauri to SN in tens of millions of years, dozens of times shorter than the accretion time for a star anywhere near Msol.

A true "first generation" star would be very hard to find. Maybe a smallish Type O could condense fast enough, yet live long enough to still be around today.
Yes, which is why most of the 'first generation' stars are in the galactic halo where all the early low mass stars are - the ones that can't become supernovae and shed their metals into the surrounding space.

And Type O stars are supernova stars - they only live for a few million years at most and then blow up. They're very rare, but we see lots of Os and Bs in the sky because they're so darn bright.
 
Type I Supernova systems are neutron stars that strip gasses from the envelope of a close binary companion, so could not some Type IIIs have enough mass stripped away that they "devolve" as it were? But whadda I know.
And Type O stars are supernova stars - they only live for a few million years at most and then blow up. They're very rare, but we see lots of Os and Bs in the sky because they're so darn bright.
Yes, I had O and B flipped in my pea brain. :rolleyes: [Note to self: be more careful with those late, late night posts] I thought those stars barely over the C limit had very long Main Sequence lives. Yes? No? :confused:
 
Originally posted by Straybow:
Type I Supernova systems are neutron stars that strip gasses from the envelope of a close binary companion, so could not some Type IIIs have enough mass stripped away that they "devolve" as it were? But whadda I know.
Type Is are *White Dwarf* stars that pull mass of their companions (usually red giants) and add that mass to themselves. When they reach 1.44 solar masses, they blow themselves apart (they become unstable above that mass), to make a Type I supernova.

I don't think giants can lose enough mass to actually 'devolve' in such cases.

Yes, I had O and B flipped in my pea brain. :rolleyes: [Note to self: be more careful with those late, late night posts] I thought those stars barely over the C limit had very long Main Sequence lives. Yes? No? :confused: [/QB]
C limit?

The lower the mass of the star, the longer the main sequence lifespan. K and M V stars that were born at the start of the universe are till in their main sequence stage, and some of the M stars have *trillions* of years left to go before they burn out. The Os and the Bs have main sequence lifespans of the order of a million to tens of millions of years, then they either shed a buttload of mass in their giant stages and become white dwarfs or they turn into supergiants and then go supernova. The As, Fs, and Gs are the ones that have a lifespan between hundreds of millions of years and about 10 billion years.
 
And are not some red giants in the Type I SN systems Type IIIs? And if they have significant mass stripped away by the dwarf, what happens to them?

Chandrasekhar limit, 3.3 M(sol), minimum for fusion all the way to iron with subsequent Type II SN. I've seen conflicting data on where that division falls. Some seem to indicate that the heaviest Type A stars are just above 3.3M, while others put it in the low Type B range.
 
Well, I've always seen the Chandrasekar limit refer to the 1.44 solar mass limit beyond which a white dwarf becomes unstable. There is a mass beyond which a massive star will burn iron and blow up as a supernova, but I don't think it's called the same thing.

I'd imagine that if a red giant were to have its entire outer envelope stripped away, you'd end up with a white dwarf there instead (since those are basically just the exposed carbon cores of red giants anyway). I don't recall ever hearing of this ever happening though (though that doesn't mean it hasn't happened).
 
Supposedly the Type I SN is cyclic if the pair are close enough. But if not, then the giant will have a certain amount of gasses stripped and then it will remain in a diminished state.

As for the C limit, 1.44 Msol is what's left after the outer envelope of gasses has been blown off in successive stages of ignition: He, C/N/O, Mg, Si/O, and finally Fe and core collapse. In order to have at least 1.44 Msol in the core to collapse into a neutron star, it would have to start out with 3.3 Msol.

As I understand it. Otherwise, Type F5 stars or thereabouts would collapse into neutron stars and there would be zillions of them.
 
Hi,

like the C limit for a white dwarf, there is a upper mass borderline for neutron stars.
This one is called Oppenheimer-Volkhoff-Border and is located somewhere between 3 and 4 solar masses. Stars of larger core mass convert to a black hole.
As Straybow stated, mass limit refers to the iron core area.

In my literatur I found a value of about 8 solar masses below that stars will decay to to white dwarfes.

AFAIK Type I SN are not cyclic because the main actor is ripped apart during this action


Regards,

Mert
 
Originally posted by Straybow:
Supposedly the Type I SN is cyclic if the pair are close enough. But if not, then the giant will have a certain amount of gasses stripped and then it will remain in a diminished state.
Novae can be cyclic. Type I SN blow up the White Dwarf - there's nothing left of it. So when you have one of those, it won't happen again


As for the C limit, 1.44 Msol is what's left after the outer envelope of gasses has been blown off in successive stages of ignition: He, C/N/O, Mg, Si/O, and finally Fe and core collapse. In order to have at least 1.44 Msol in the core to collapse into a neutron star, it would have to start out with 3.3 Msol.
Nope. I think the limit for a star to become a neutron star is about 8 solar masses. Don't forget that stars between about 2 and 8 solar masses shed a heck of a lot of mass in their red giant phases before they end their lives as white dwarfs.

Also, if the star is burning heavier elements than helium in its core, then it's a massive supergiant and it's going to end up as a supernova anyway - I think if the star is on that path then it has to go all the way to the attempted Fe-burning that results in the supernova - it can't just stop halfway. And if it's massive enough to end up on that evolutionary path and die as a supernova, it'll either become a neutron star or a black hole.

As I understand it. Otherwise, Type F5 stars or thereabouts would collapse into neutron stars and there would be zillions of them.
I think we're looking at B and O V stars as being the only ones that can go supernova. Even a 7 solar mass star is only early B V.
 
"AFAIK Type I SN are not cyclic because the main actor is ripped apart during this action
"

"Novae can be cyclic. Type I SN blow up the White Dwarf - there's nothing left of it. So when you have one of those, it won't happen again
"

"I think we're looking at B and O V stars as being the only ones that can go supernova. Even a 7 solar mass star is only early B V."

D'oh! You are correct, it is "ordinary" nova binaries that can be cyclic. And if 1.44M F5V is too small for SN, so would 3.3M (mid A-range). I wuz not thinking clearly. This is all stuff which gets confused rather easily.

I've always loved the story of Chandrasekhar. He was a promising self-taught physics grad, granted a fellowship at Oxford or something. To pass the time on the ship from India to Britain he calculated the theory which became his signature work.

This guy accomplished more in a week or so of spare time than any of us will in our whole lives.


Suitably humbled at the thought, the narrator continues. I can't find a reference that clearly says what the original mass (or range of masses) would be in order to end up at the C limit in Dwarf stage. Many googles later&#133

HyperPhysics: White Dwarfs and Electron Degeneracy indicates that all stars 4M or less are too small to fuse Carbon. It doesn't say how much of that mass is lost when the carbon core collapses into degenerate matter.

Therefore at 4M it can't develop an iron core that could collapse into a neutron star. It would seem, though, that stars above that limit might still be too small to fuse all the way to iron.

The HyperPhysics: Astrophysics Index shows stars 4-8M becoming either neutron stars or black holes, which seems to ignore masses large enough to fuse Carbon but insufficient to fuse large quantities of heavier elements leading to a massive Fe core.

As previously stated, 4M is too small to form NS, as that would put the boundary in the A range. Death of High Mass Stars indicates an initial mass of 5M will produce a neutron star, which again seems too low by far (either the largest As or smallest Bs). This could be a limit for Type I SN, that a smaller star would not produce a WD massive enough to fuse Iron under the added mass from a companion's envelope.

:confused: Any thoughts on that?

The Hyperphysics Index also shows the possibility of collapse into a neutron star without a supernova event. It hardly seems possible to have a quiescent change when such energies are involved. On the other hand, if 4M - 8M stars form Red SGs but collapse without SN event into WD, that would make sense.

Also, Blue SGs can go straight to Type II SN (SN1987A) without a Red SG phase. I think between these two lines of evolution maybe that's what was meant. Chalk that up to sloppy editing; someone should write them a courteous email.

Following the link shown as HyperPhysics: "Red Supergiant" indicates that a mass of 15M will form a Red Supergiant in the triple alpha phase. It also implies that a Red Supergiant can become either a NS or a BH. I suspect 15M might be the limit for Black Hole formation. We have to more than double the mass of iron in the core from 1.44M to ~3.3M, so maybe it takes a near doubling of the initial mass. 8M snd 15M could be those initial conditions.

All those Astro-Eggheads need to get their data straight for us armchair Einsteins. ;)
 
Supergiants are the stars that are burning heavy (heavier than Helium) elements in their cores. They have to be high mass, from what I've seen 10+ seems to be about right, certainly 15 solar masses is in the right ballpark (Antares is 15 solar masses, IIRC)

I think the honest answer is that stellar physicists aren't really sure where the exact boundaries lie (they don't even agree on how to exactly define the various spectral types). And remember that spectral types are just that - they're divisions of the types of absorption spectra produced by a star's atmosphere. As such, they can't really tell you much about how the star will evolve - only knowing the mass can do that.
 
Yeah, many sources say "about 1.4M¤" for C limit and an even more vague "about 2-3M¤" on the maximum for NS. I found one source that posited 11M¤ as the initial size to exceed C-limit post-collapse.

Shoot, there isn't even that much agreement on mass for the Type V spectral boundaries above F. Too many Bs and Os just aren't close enough to get a good look at 'em or pin down their distance.

I found a couple mentions of new Type V classes L and T, added below M. L stars burn brightly (in the infrared) for unknown millions of years with D and Li fusion but never sustain proton fusion. T are essentially large Brown Dwarfs, but some distinction is being made. L go up to 70Mj or ~.066M¤; lower boundaries uncertain.

I guess our mnemonic is now "O, Be A Fine Girl, Kiss Me Like That!" ;)
 
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Yeah, L and T are brown dwarfs
. IIRC T are actually the older/dimmer/cooler/less massive brown dwarfs - you get things like methane bands in the spectrum because they're so cool.

If you can access that, I wrote up some rules on how to generate Brown Dwarfs for Traveller (based on some of the scientific papers) as a JTAS article.

I guess the full spectral type mnemonic would go something like:

"Wow! Oh Be A Fine Girl, Kiss Me Like That Right Now Sweetie!"
 
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