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Old 02-18-2017, 04:13 PM   #1
Pragmatic
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Default [Space] RAW to get two roughly Earthlike planets?

I think I tweaked the rules once by having a close-orbit binary system (so not much more mass, but higher luminosity, which led to larger "Goldilocks" zone), something that I seem to recall was available in Space 3E.

Is there some way of getting "warm/chilly" or "hot/cool" combos of roughly Earthlike planets?
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Old 02-18-2017, 04:16 PM   #2
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Default Re: [Space] RAW to get two roughly Earthlike planets?

If I understand what you are asking, you want to know if space 4e lets you stick two planets in the goldilocks zone? The short answers is yes, though I can't give you the math right now.

Or are you asking a different question?
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Old 02-18-2017, 04:30 PM   #3
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Default Re: [Space] RAW to get two roughly Earthlike planets?

Two planets that aren't too far off of the human-norm.

The problem is, when you start getting past Earth orbit, the temperature drops FAST.

I did it in 3E by placing two Sol-sized suns in a close binary. 3E, IIRC, had a rule where you could add masses and luminosities. This stretched the Goldilocks zone enough so the next orbit wasn't too far into the cold/frozen area.

Is that possible with the rules in 4E, or has the science (and accompanying GURPS modeling) changed?
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Old 02-18-2017, 05:51 PM   #4
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Default Re: [Space] RAW to get two roughly Earthlike planets?

some estimates of our own suns Habitable zone put Venus and Mars on the edges of it
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Old 02-18-2017, 06:09 PM   #5
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Default Re: [Space] RAW to get two roughly Earthlike planets?

I managed it once quite by accident in 4e Space for Alpha Centauri B. They were both habitable, though one was quite hot and arid with a smaller than normal hydrosphere, the other was colder than average with a large hydrosphere. I named the planets Tatooine and Hoth, claiming that Alpha Centauri B was mapped/had planets named by sci-fi geeks. :) (Officially Tatooine beat out Arrakis by a very slim margin.)
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Old 02-18-2017, 06:31 PM   #6
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Default Re: [Space] RAW to get two roughly Earthlike planets?

It is possible to get two (temperate) habitable planets orbiting the same star. It just requires luck getting the orbits closely bunched together. Atmospheric mass and hydrographic coverage can moderate the temperature further, so its even possible to get two normal climate worlds in the same star system.

Also, there are trivial cases (two planets orbiting different stars, two moons of the same gas giant).
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Old 02-18-2017, 06:59 PM   #7
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Default Re: [Space] RAW to get two roughly Earthlike planets?

Quote:
Originally Posted by TGLS View Post
It is possible to get two (temperate) habitable planets orbiting the same star. It just requires luck getting the orbits closely bunched together. Atmospheric mass and hydrographic coverage can moderate the temperature further, so its even possible to get two normal climate worlds in the same star system.

Also, there are trivial cases (two planets orbiting different stars, two moons of the same gas giant).
Don't forget binary planet: worlds of similar sizes, both bearing life, one as the moon of the other. Panspermia almost certainly happens in this case.
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Old 02-18-2017, 10:46 PM   #8
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Default Re: [Space] RAW to get two roughly Earthlike planets?

Kepler has found some exoplanets in very close orbits.
Quote:
Originally Posted by https://en.wikipedia.org/wiki/List_of_exoplanet_extremes#Orbital_characteristics
Smallest semi-major axis difference between planets
Kepler-70b and Kepler-70c[30]
Kepler-70
0.0016 AU (about 240,000 km)
During closest approach, Kepler-70c would appear 5 times the size of the Moon in Kepler-70b's sky.

Smallest semi-major axis ratio between planets
Kepler-36b and Kepler-36c
Kepler-36
11%
Kepler-36b and c have semi-major axes of 0.1153 AU and 0.1283 AU respectively, c is 11% further from star than b .
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Old 02-19-2017, 12:04 AM   #9
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Default Re: [Space] RAW to get two roughly Earthlike planets

Another possible option would be a gas giant (or brown dwarf) with two habitable moons. You probably need a bright star so that the life zone extends outside the unlikely-to-have-very-many-moons zone.

Yet another possibility, not provided for in the rules, is co-orbital worlds. Either of one another directly in some sort of horseshoe orbit, or both gravitationally bound as Trojan objects to a large gas giant or brown dwarf.
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Old 02-19-2017, 01:34 AM   #10
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Default Re: [Space] RAW to get two roughly Earthlike planets?

You could widen the Goldilocks zone by assuming a larger, hotter star, on the high of the scale (F, A, B, or O). The hotter the star, the wider the good zone.

The problem is that presumably such stars are too short-lived for habitable worlds to happen naturally. That makes some assumptions that may or may not be true, though. Certainly, I wouldn't be shocked to see habitable worlds around an F or even maybe an A, everything else being equal.
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