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Old 08-11-2022, 04:51 PM   #1
cupbearer
 
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Default Number of habitable worlds within170 light years?

Hi,

I know nobody can really answer this with true certainty, but what do you think a reasonable amount of habitable worlds would be to place in a campaign if you traveled in every direction up to 170 light years away?
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Old 08-11-2022, 05:33 PM   #2
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Default Re: Number of habitable worlds within170 light years?

There are more than 60 G-type stars (like Sol) within 50 parsecs (just under 170 ly) from Earth:

http://www.solstation.com/stars3/100-gs.htm

There are many many many M-type stars (Red Dwarfs likely to have habitable zones) within 50 parsecs. It's up for debate, though, whether these stars are really likely to have habitable worlds:

http://www.solstation.com/stars3/100-ms.htm#40-50

And maybe the likeliest to have habitable worlds are K-type stars, with an estimated >200 within 50 ly and maybe as many as 2,000 within 100 ly.

http://www.solstation.com/stars3/100-ks.htm

Hope these pages help!

EDIT: In other words, probably far, far more than it would be possible to stat for any playable game! Guesstimate 10% of these stars host habitable worlds and you're still looking at more than a thousand habitable worlds within 50 parsecs at the very least.

Last edited by JulianLW; 08-11-2022 at 05:37 PM.
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Old 08-11-2022, 05:41 PM   #3
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Default Re: Number of habitable worlds within170 light years?

I ran the GURPS Space generator over data from the XHIP catalogue. Disregarding a lot of synchronously-rotating planets of M and late K stars that I didn’t think would actually be habitable, and adopting a somewhat higher bar for habitability than the standard Habitability rating, I got one thousand habitable planets within 175 light years.

That’s optimistic, but not incredible.
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Last edited by Agemegos; 08-12-2022 at 02:02 AM. Reason: typing errors, including “155” for “175”
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Old 08-11-2022, 05:44 PM   #4
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Default Re: Number of habitable worlds within170 light years?

Quote:
Originally Posted by JulianLW View Post
There are more than 60 G-type stars (like Sol) within 50 parsecs (just under 170 ly) from Earth:

http://www.solstation.com/stars3/100-gs.htm

There are many many many M-type stars (Red Dwarfs likely to have habitable zones) within 50 parsecs. It's up for debate, though, whether these stars are really likely to have habitable worlds:

http://www.solstation.com/stars3/100-ms.htm#40-50

And maybe the likeliest to have habitable worlds are K-type stars, with an estimated >200 within 50 ly and maybe as many as 2,000 within 100 ly.

http://www.solstation.com/stars3/100-ks.htm

Hope these pages help!

EDIT: In other words, probably far, far more than it would be possible to stat for any playable game! Guesstimate 10% of these stars host habitable worlds and you're still looking at more than a thousand habitable worlds within 50 parsecs at the very least.
Thank you very much
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Old 08-11-2022, 05:44 PM   #5
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Default Re: Number of habitable worlds within170 light years?

Quote:
Originally Posted by Agemegos View Post
I ran the GURPS Space generator over data from the XHIP catalogue. Disregarding a lot of synchronously-rotating planets of M and late K stars that I didnít think would actually be habitable, and adopting a somewhat higher bad for habitability than the standard Habitability rating, I got one thouasnd habitable planets within 155 light years.

Thatís optimistic, but not incredible.
Awesome thank you
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Old 08-11-2022, 07:15 PM   #6
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Default Re: Number of habitable worlds within170 light years?

A lot depends on your definition of habitable, and on some assumptions (I would note that Earth has not been human-habitable for most of its lifespan, and we have far less information about alien planets)
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Old 08-11-2022, 09:23 PM   #7
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Default Re: Number of habitable worlds within170 light years?

I use K, G, and F type stars for hunting down habitable worlds. A generous estimate is likely to be 50% of the stars have a planet in the habitable zone, with 50% of those planets being habitable without some form of terraforming.

That said, in my own space opera setting I have a habitable planet in each of those that has a stable zone (F types with orbiting white dwarfs - like Procyon - don't count) - and even those whose planets aren't habitable still get inhabited by humans in pressure domes. So even the M-types are inhabited, even if not inhabitable.

(A-types like Vega aren't likely to have habitable planets, due to being too young, if they have planets in the first place.)
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Old 08-11-2022, 09:29 PM   #8
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Default Re: Number of habitable worlds within170 light years?

Fascinating! Why 170 ly? Can we scale up these numbers to larger regions? What's the percentage of stars in the galaxy that would have habitable planets, using these same assumptions? (I'm presuming the core might have a lower percentage of habitable systems...).
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Old 08-11-2022, 10:05 PM   #9
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Default Re: Number of habitable worlds within170 light years?

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Originally Posted by SydneyFreedberg View Post
Fascinating! Why 170 ly?
At a guess, travel at 1pc per week would take almost exactly 52 weeks to travel from the center to the rim. 170ly / 3.26ly/pc = ~52.15pc.
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Old 08-12-2022, 02:06 AM   #10
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Default Re: Number of habitable worlds within170 light years?

Quote:
Originally Posted by Anthony View Post
(I would note that Earth has not been human-habitable for most of its lifespan…)
What, because of the lack of oxygen and toxic concentration of CO₂ in the atmosphere?

Little thing like that!
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