Two T-type planets in the habitable zone?

[ChalkLine]

Okay, I'm writing a scenario that requires two habitable planets in a system with outside survival conditions that don't require much more than a respirator. So I'm scratching my head wondering how to pull it off.

I first thought of a captured moon but that doesn't seem to work. Then I thought about having both planets as satellites of a gas giant, but I don't want the planets to be tidally locked. If they're not tidally locked and in a polar orbit, it means I end up with my two satellites in darkness most of the time. One planet could be tidally locked, but I'd prefer the other to have a normal day/night cycle.

Any suggestions?

 

[Elv]

By carefully picking the star, hydrographics, etc, you should be able to put one at the extreme inner edge of the habitable zone and the other at the extreme outer edge, having one very hot and one very cold. Would that do?

John

 

[atpollard]

By carefully picking the star, hydrographics, etc, you should be able to put one at the extreme inner edge of the habitable zone and the other at the extreme outer edge, having one very hot and one very cold. Would that do?

John

More white quartz sand on the hot world (to reflect more light/heat) and a little "greenhouse effect" on the cold world could pull the temperatures a little closer to normal.

Combine that with the right axial tilt and both worlds could have an earth-like zone. It could be the equator on the cold world being like Canada on Earth and the arctic circle on the hot world being like the Tropics on Earth.

 

[robject]

One could be orbiting a near companion star in a close orbit.

You could have a rosette of three worlds of about the same mass, equidistant, in the same orbit. It's not natural (i.e. someone 'engineered' the system), but it would work.

Touching on an earlier post, have an Earth+Mars-like setup, where the world in the Martian orbit has been terraformed enough to support life.

Or, just bump out 'Earth' and 'Venus' a little bit.

 

[Plankowner]

I like Robject's idea of a binary star system. You can put the stars as close as 3 AU from each other and still have occupied habitable zones around them (assuming G type stars like our sun). Put them a bit farther apart for longer travel times and you are good to go.

Inner and Outer edge of the Habitable zone works too. I suggest an "F" color star since it is brighter and gives a bigger habitable zone. Surface conditions or atmospheric taint could easily adjust the temperature up or down to make both of them shirt sleeve planets (at least parts of the planets).

If you put Venus where Mars is now and gave it a more Earth-Like atmosphere, it would be pretty habitable, at least at the Equator...

 

[KrasnyKot]

Twin Planets!

You should try constructing a larger planet (size 8-A) orbited by a smaller one (size 4-6).
Fudging with the UPP rules (calculate the "wanted" die-rolls) should give two "planets" (well, one would be classified as a moon) with breathable atmospheres and acceptable hydrospheres.
I did it before using the UPP-rules of Scouts.

 

[kafka47]

Not to mention that most of the worlds of the Traveller Universe are handwaves care of the Ancients. Terra-like worlds given the worldgen rules are pretty rare, however, not impossible for two to be in the same system...so not using the handwave, I would have to question how habitable do you consider habitable. Is the Sahara or Antarctic still habitable (or Type T) for you? If so, I can see easily see two, if the star is right...

 

[Gadrin]

nice thread, if you flesh it out in more detail, please share.

 

[Fritz_Brown]

Which system are you using to generate the worlds? It makes a difference, as CT doesn't allow for 2 orbits in the Habitable zone. It is also tough to get a binary system with two habitable zones (unless the stars are pretty far apart - out in the 10th orbit or further) mainly because the second star is usually a dwarf where all the orbits are Outer zone.

In CT, though, you can put captured planets in the habitable zone (I have this happen occassionally - the H zone has a nice planet, and there is a captured planet .3 orbits out and still in the Habitable zone). Also, CT doesn't talk about tidally locked moons (IIRC) - that would be something you introduced for your desired level of realism.

(BTW, I have had captured planets come out .1 orbit from another planet. I will keep at least one of those for a Gor scenario. )

 

[su_liam]

Make the inner world large and dry with a low pressure atmosphere to minimize greenhouse effect. Make the outer world small and wet with a high pressure atmosphere to maximize greenhouse effect. Optical thickness is roughly proportional to (surface pressure)/(gravity), that is to say, roughly the mass of the atmosphere per unit of surface area.

 

[spank]

Two hab worlds

try using this as a starting point

Sun f5 class V luminosity 1.5594
orbit 4

*456****
surface temp 26.598c
hex row
1 41.598
2 36.598
3 31.598
4 26.598
5 21.598
6 16.598
7 11.598
8 06.598
9 01.598
10 -3.402
11 -8.402

orbit 5

*881****
Surface temp -1.16c
hex row
1 19.84
2 12.84
3 5.84
4 -1.16
5 -8.16
6 -15.16
7 -22.16
8 -29.16
9 -36.16
10 -43.16
11 -50.16

 

[JustinInOz]

Parameters to play with

G'Day,

Changing the albedo of a planet and the green house effect will prety much give you what ever temperatures you want. Given an orbit on either side of the habitable.

You could probably have 3 habitable worlds without too much hand waving. All you need is a surface or atmosphere that has a high/low albedo. If that does not work mix it up with an atmosphere having/lacking CO2 and/or CH4 and you are set.

Lots of CO2 could come from polution or a prebiotic atmosphere. Or an atmosphere with an alien biology.

Download the following spread sheet:

icp.giss.nasa.gov/education/geebitt/

Play around with the paramenters and you will quickly see what I mean. I use the one with the mid range amount of complexity. One is too simplistic and I do not trust climate modellers enough to use the third one.

 

[DaveChase]

Off the top of my head, there was a system in OTU (do not remember what version) that had 5 worlds in the same habitable orbit zone. Something that the Ancients did.

Could do the same or even use the same system but there are only 2 worlds as the other 3 have been reduced to asteroids. Then both planets would have regular metor strikes and craters.

Just some of my thoughts on the fly.

Dave Chase

 

[Starviking]

Off the top of my head, there was a system in OTU (do not remember what version) that had 5 worlds in the same habitable orbit zone. Something that the Ancients did.

Could do the same or even use the same system but there are only 2 worlds as the other 3 have been reduced to asteroids. Then both planets would have regular metor strikes and craters.

Just some of my thoughts on the fly.

Dave Chase

I think that's the Rosette at Tireen, somewhere in Vargr Space.

The system in The Keith's FASA adventure "Uragyad'n of the Seven Pillars" had two habitable planets - a hot desert world and a glacial world.

Of course, moon-festooned gas giants in the habitable zone have lots more potential...

Starviking

 

[atpollard]

Of course, moon-festooned gas giants in the habitable zone have lots more potential...

I don't think that a gas giant can exist in the habitable zone since the higher temperature would cause all of the hydrogen to escape into space - thus no more gas giant (something about the average energy of the particles being grater than escape velocity).

 

[Plankowner]

Habitable Zone Gas Giants

Gas giants seem to be in every possible orbit. Some of the first extra-solar planets discovered where so-called Hot Jupiters. They orbit less than 0.1 AU from the star in a few days.

They definitely have hydrogen and they are quite hot. If they can exist inside the habitable zone, there is no reason they cannot exist within the habitable zone. I don't have references off the top of my head, but I THINK we have discovered one already.

 

[atpollard]

Gas giants seem to be in every possible orbit. Some of the first extra-solar planets discovered where so-called Hot Jupiters. They orbit less than 0.1 AU from the star in a few days.

They definitely have hydrogen and they are quite hot. If they can exist inside the habitable zone, there is no reason they cannot exist within the habitable zone. I don't have references off the top of my head, but I THINK we have discovered one already.

When basic physics contradicts reality, I yield to reality.
... but I bet that something funky is going on with "Hot Jupiters" and there is more to learn about that. For now, ignore my previous post.

 

[Plankowner]

I agree, there is a LOT to learn there.

As I remember, most of the planetary scientists found it hard to believe in Hot Jupiters, even when the observational data was confirmed. SOMETHING is going on there, it will be interesting to see what they decide is keeping everything in place.

 

[aramis]

We, as a species, don't know enough yet to make a realistic system generator that will cover all the bases without breaking some restriction we think still fits...

As more and more data is gained on extrasolar worlds, the less normal our "normal little star" seems by virtue of its companions.

So if you want to put 2 or even three habitable worlds, play with the albedo, and have fun with it, and don't worry, some ******* will come along and claim it's impossible, when we keep finding stuff that the Snarky pseudo-scientists (and a good many of the real scientists) of the world flat out claimed couldn't exist a mere 15 years ago...

 

[Peter Newman]

Consider this as well - If Venus was where Mars is, it would have held on to enough atmosphere and water to be far more habitable than Mars is, while if Mars was where Venus was it would probably have avoided the whole runaway greenhouse problem, since its gravity just isn't strong enough to have held onto that much atmosphere. You could, just barely, have 3 habitable planets in a system, much less two. I'd love to see what would happen if you travelled back in time a few billion years, switched the postions of Venus and Mars (correcting velocity so the new orbits were stable), and than returned to the present, popping out along the way to check on their progress.