Habitable Zone for Spectral Type O / B Stars?

[LiminalMask]

Hi. I can't seem to find anything on the habitable zone orbits for type O and B stars. The rules only seem to go up to A in spectral type. I rolled a world with an O9 III star and I'm not sure where to place the HZ.

Does this mean type O and B stars cannot support life? This seems odd because A) The Spectral Type generation table comes long after you've made the world in question, so it would seem like a waste of time and B) Even really big stars could theoretically have a HZ far out in the Outer or Remote orbits.

Thanks!

 

[HG_B]

I copied this explanation from a post here many months ago:

Spectral Class O Stars (Blue Giants) -- These are so big, even as main sequence, that they're called giants. They lose whole suns worth of mass as solar winds (solar hurricanes?) blowing their outer layers off as they age. Lifespans of only thousands of years before they die spectacularly.
They average about 25 solar masses. 0.0000025% or 1 star in 40,000,000.

Spectral Class B Stars -- Average about 5 solar masses. Still very hot and very short lived. Probably not enough time in their lives for planets to form out of the gas and dust orbiting them. 0.075% or 1 star in 1300

Spectral Class A Stars -- Still too hot, big, and short lived for life-bearing planets to have time to form around them -- life might get as far as oceans of yeast and stuff before they die. Average about 1.7 solar masses. 0.75% or 1 star in 130.

 

[aramis]

Really, Type O and B stars shouldn't have planets, and shouldn't be on the maps except by GM fiat. (≤1:1000 frequency). The no planets issue is one of "they're just too young and short lived."

And, even if they do have planets, those planets should all be rocks or GG's; nothing habitable... because life has not had time to evolve.

I've looked into it a bit, in the past...
As for type B, in my EC Worldgen PDF I have a compact table showing the vaporized and habitable orbits for type B. (Table's on page 4.)

For Type O, just use the B0 line, but add 1 for O8-O9, 2 for O6-O7, 3 for O4-O5, 4 for O2-O3, and 5 for O0-O1.

 

[rancke]

Really, Type O and B stars shouldn't have planets, and shouldn't be on the maps except by GM fiat. (≤1:1000 frequency). The no planets issue is one of "they're just too young and short lived."

And, even if they do have planets, those planets should all be rocks or GG's; nothing habitable... because life has not had time to evolve.

I acknowledge that all this is true, but I still really, really want to use Jack Vance's Rigel Concourse (though perhaps around some other blue supergiant) in Traveller. Probably not going to be allowed to sneak it into the OTU ever. Ah well...

Anyway, the point I wanted to make was that reality is well enough in its place, but if an imaginary star system is sufficiently evocative, reality can just take a back seat (as far as I'm concerned).


Hans

 

[LiminalMask]

Thanks, everyone, for the insight. Aramis, that's a helpful document, thank you. It still strikes me as odd that Class O and B stars are possible in the system generation rules if, ultimately, they are not really conducive to life or even colonization.

My thought about this is twofold: change the rules so that O and B stars are not possible, instead shift the table up so A stars replace them (and probably add another class M at the bottom)...

Or, assume that any habitation in an O or B world must be settlers or transplants, and either have the required technology to survive the "solar hurricanes" or be sophonts adapted to such conditions.

 

[Starviking]

I acknowledge that all this is true, but I still really, really want to use Jack Vance's Rigel Concourse (though perhaps around some other blue supergiant) in Traveller. Probably not going to be allowed to sneak it into the OTU ever. Ah well...

Anyway, the point I wanted to make was that reality is well enough in its place, but if an imaginary star system is sufficiently evocative, reality can just take a back seat (as far as I'm concerned).

Hans

The Rigel Concourse was suspected of being constructed in Jack Vance's Demon Princes series. Throw a meddling Ancient in and voila! Doesn't even have to be the official Ancients - lots of prehistoric space-going races in Charted Space.

I recall a Flandry story by Poul Anderson which featured a habitable planet around a bright primary - the planet was captured in a close encounter with another system. Could work.

 

[fusor]

The habitable zone for an 09 III (which would be a stupendously rare star anyway) would be so far away from the star (100-300 AU) that even if a planet could potentially form there, it wouldn't be able to - there'd be too little material spread too thinly for it to form from that far from the star, and by the time any kind of accretion even started the star would explode as a supernova.

 

[LiminalMask]

The habitable zone for an 09 III (which would be a stupendously rare star anyway) would be so far away from the star (100-300 AU) that even if a planet could potentially form there, it wouldn't be able to - there'd be too little material spread too thinly for it to form from that far from the star, and by the time any kind of accretion even started the star would explode as a supernova.

Just goes to show that modifying the generation table is the best way to go and leave the O and B stars to specific scripted encounters.

 

[Peter Newman]

Recent evidence suggests that loose planets are fairly common. That may mean that the chance of a solar system picking one up are better than Traveller system generation allows. It also seems likely that a more massive star has a better chance of picking up a rogue planet, simply because of its bigger and stronger gravity well.

Therefore feel free to put older planets around young massive stars, as long as you explain them as captured planets. Giving them fairly eccentric orbits seems likely.

 

[bubbacleese]

...older planets around young massive stars...

Just after being captured, what did the old planet say to the young massive star? :devil:

Ok you wonderful imaginative science fiction role players; let's see what good answers you can come up with. Don't think of this as a competition but do try your best. Everyone is NOT limited to just one answer.

 

[Enoki]

Just introduced that young star to a classic rock:

http://www.youtube.com/watch?v=ipqqEFoJPL4

 

[Gray Lensman]

Just introduced that young star to a classic rock:

http://www.youtube.com/watch?v=ipqqEFoJPL4

Great Song Bro!

Really, Type O and B stars shouldn't have planets, and shouldn't be on the maps except by GM fiat. (≤1:1000 frequency). The no planets issue is one of "they're just too young and short lived."

And, even if they do have planets, those planets should all be rocks or GG's; nothing habitable... because life has not had time to evolve.

I've looked into it a bit, in the past...
As for type B, in my EC Worldgen PDF I have a compact table showing the vaporized and habitable orbits for type B. (Table's on page 4.)

For Type O, just use the B0 line, but add 1 for O8-O9, 2 for O6-O7, 3 for O4-O5, 4 for O2-O3, and 5 for O0-O1.

And I have had a lot of fun in my homespun campaign thanks to Aramis' work.

 

[bubbacleese]

Three days and not one reply. Maybe you were all busy this weekend.

 

[RainOfSteel]

It's late to the party, but just to be clear, O type stars have such immense solar winds that no planetary disk could form, much less planets of any kind.

You would be stuck with captured objects, at best, for the very short lifespans of these objects.

Also, O type stars appear at a rate of one in three million stars, so they're very rare.

Essentially, if O type stars never appear in a game, you're doing okay.

 

[aramis]

It's late to the party, but just to be clear, O type stars have such immense solar winds that no planetary disk could form, much less planets of any kind.

You would be stuck with captured objects, at best, for the very short lifespans of these objects.

Couldn't the disk potentially have formed a gas giant or two prior to their ignition? After all, they can form multiple star clusters, as exemplified by Sigma Orionis A-E...

A:O9V primary
B:B0.5V 90AU
C:A2V 3900AU
D:B2V 4600AU
E:B2Vp 15000AU

from http://www.daviddarling.info/encyclopedia/S/Sigma_Orionis_star_cluster.html :

A young open cluster, 1 to 5 million years old, that is part of the Orion OB Association, adjacent to the Horsehead Nebula; the star Sigma Orionis lies at its center. Within this cluster have been identified a number of free floating brown dwarf and large planet candidates.​

Certainly strange stuff... the distances are in thousands of AU. They are only weakly gravitationally bound, if at all. σ Ori 70 is "sitting 36,000 times farther away from any its nearest stellar neighbor than Jupiter is from our Sun." - which is some 180,000 AU.

σ Ori 47, 52, 56 & 60 are confirmed members of the Sigma Orionis cluster, and are below the duterium burning mass limit. (ref to table)

Note, tho, the found planetary candidates are further out than σ Ori E... so lower mass captures are VERY possible...

references:
http://en.wikipedia.org/wiki/Σ_Orionis_A (wikipedia cites SIMBAD)
http://simbad.u-strasbg.fr/simbad/ (Sigma Orionis data confirmed from here using search)
http://www.daviddarling.info/encyclopedia/S/Sigma_Orionis_star_cluster.html
http://stars.astro.illinois.edu/sow/sigmaori.html confirms wikipedia orbital distance data.
http://arxiv.org/abs/astro-ph/0410678 discusses sigma orionis planet candidates as class T and extremely red.
http://www.iac.es/proyecto/vlmbd/ provides more Sigma Orionis planetary refs.
http://www.sciencemag.org/content/290/5489/103.full?ijkey=IbRxROH96pg.g&keytype=ref&siteid=sci Science Magazine article on Sigma Orionis planetary candidates
http://www.alcyone.de/SIT/bsc/HR1931.html gives ra and dec for Sig Ori AB and various separations for A-E in arc sec...

 

[Fritz_Brown]

Which system were you using to do the generation?

 

[lolnoobzor]

The idea of 'planting' an O/A type hyper/supergiant star into a sector I'm building had captured my imagination until I realised that the regular flares can wipe out any of those unlucky 'old' planets you were talking about...

And that's before taking into account the occurence of pressure release that happens if the star passes over the Eddington limit (the point at which radiation 'pushes' more than gravity 'pulls' the star's outer layer), sometimes shedding dozens of solar masses in a single event (yay wikipedia). Then I'd thought of something that bugged me even more.

The kind of star I wanted to put in is not only extremely rare, but it only occurs in areas of active star formation, which would place the entire sector in some of the least hospitable areas of the universe, with most systems not even having cooled off enough for gas to aggregate into planets. Actually an O-type's radiation is enough to not only blow it's own accretion disk away, but to prevent nearby stars from keeping theirs!

I'm still not sure I might not want to put it in anyway for fun's sake, but 'realistically' it would mean the sector's sitting inside a gas cloud, with every planet constantly buffeted by enormous radiation etcetc.

Actually an idea to make it playable just struck me: an entire sub-sector amber/red-zoned around a gigantic O-type/OB cluster, buffeted by radiation and winds of super-heated gas. The amber radius would indicate the area where planetary life becomes dangerous/impossible, except for a few planets with incredible magnetic fields on the edge of this area (no point in designing all this if there's no reason to come adventuring eh?), then the red zone limit would be a death sentence for anyone jumping in. Possible adventure seeds could be recovering lost ships, escorting/conducting scientific surveys, finding some ancient (Ancient?) treasure trove hidden in the last place anyone sane would look, resupplying an advanced outpost/waypoint...

To get into specifics, I'm not an astrophysicist but I'll try to eyeball some kind of distance from wikipedia's data: O-type stars radiate over 1 million times our sun's output, so even if it's a 'weak' one, we could say a planet has to be at least 1 million AU, or 5 parsecs, away to 'only' receive radiation equivalent to our sun's radiation (a very gross approximation, I know). So if it's a 'small' O-type, I'd put the amber-zone limit, say at 3 parsecs around it, then maybe red-zone at 1 parsec around the star? You may of course reduce/increase the range depending on the requirements for the TU you're building - in fact the interdiction doesn't have to work as a sphere (well, actually a circle but since we're being 'realistic'...) around the star, since gas clouds could protect some of the surrounding systems.

By that same reasoning, with a giant O-type you would have to approx double/triple those distances (more if it's reaaaally big), and imagine the whole area around the star as a small nebula, possibly an OB cluster. The cluster idea would make extending the danger zone over several parsecs a lot more plausible too, since the lone star's radiation should be fairly attenuated from the nebula's gas clouds. Though a lone hypergiant LBV should justify it's danger zone quite well from what I've read about it...

An interesting side effect I see of setting up a 'mininebula' around an O-type or two IMTU is that it makes piracy a lot more plausible (dense gas clouds would make ambushes in space actually possible!), especially if there's a system of gas-collecting waypoints and gas giants providing a reason for merchants to go through there (a shortcut? only possible trade route between two points?). I think I'll try to shoehorn this into the sector I'm making - suggestions/ideas/criticism are welcome!

I also have to admit I'm surprised at Aramis' post, which means gas giants can survive in systems as close as one parsec to the O-type! I'd have thought the radiation would slowly blow the gas away, even at those distances. Maybe those gas giants are too 'young' to have yet lost their atmo? I guess that applies to everything in that corner of the galaxy though... Or they might have their own magnetic fields to protect 'em.

 

[Merxiless]

When you say 1 million times, you're talking whole body 720 degrees, right?

Because of inverse squared law, it'll drop off fast at distance. 5 psec seems like a bit much,but as you say, you're fluffing it.

I like the basic ideas though, but it begs the question, knowing if something goes wrong rescue is weeks away who builds something in a place so dangerous?

But, it would be a cool setting for adventures. Clean up the math, that's a novel, I think.

Luck.

 

[MorituriMax]

I thought the whole point of Traveller was to come up with good explanations as to why a given planet with trillions of inhabitants was size 2, and so forth.. same for O and B stars, there would BE a reason they occurred but you have to be imaginative to come up with an awesome reason.

As for putting it in the charts if it is then impossible to get that result, well, fine, Challenge accepted.

 

[flykiller]

Just after being captured, what did the old planet say to the young massive star?

you light up my life zone.