Now, I haven't read the whole thread so maybe I've missed something, but would it not be possible to just make the star hotter, to solve that the heat problem at least?
Originally Posted by Jalyha
No, I mean that the distance star/planet is about the same as ours. Your planet hill sphere is bigger because it's more massive.
Yes it's possible to have a hotter star but it also mean a more massive star that would have an impact on the hill sphere. Another possibility is the white dwarfs because they are small and very hot but they don't emit a lot of light.
Yes and no. Okay... highly simplified, so less than 100% accurate, but still understandable, here we go:
Originally Posted by Lingon
A star is basically just gas, held together with gravity. Early in life the star is contracting and is not yet hot enough or dense enough for nuclear reactions. Heat is generated by the contraction (hydrostatic support). Then, for most of its' life, nuclear reactions cause heat and radiation. Toward the end of life, most of the nuclear fuel in the core has been used up. It has a series of inefficient nuclear reactions for heat. After a long time, the reactions no longer generate sufficient heat to support the star against its own gravity, the star will collapse.
So what does that mean? Well... we have gas, energy, gravity, mass, light and heat. The problem is...
The light and heat (which is what we want) is created by the reactions - ENERGY.
You can't *create* energy. All the energy in the universe is already there. What we usually *call* energy is just a reaction, caused by interactions between things which have mass (You'll recognize E=Mc2. E is energy. M is Mass.).
What's interacting to cause these reactions is the atoms in the gasses (which have mass). The denser they are, the denser they get, the more efficient reactions, which equals more heat.
Denser stars will also have more MASS.
Which means HOTTER stars will have more mass.
Now the MASS of an object directly influences its' gravitational pull - its' hill sphere. That's how far away an object can be to be pulled into orbit. That gives us everything that can be pulled into orbit around your star/sun... planets, asteroids, etc.
As the mass increases, the energy (reactions) increase, increasing the heat, but also expanding the "hill sphere" and pulling in more objects in a larger radius.
*insert lots of stuff about giant rocks crashing, imploding, exploding, etc...*
Anyway. The larger objects in orbit - PLANETS have a lot of mass.
"Now the MASS of an object directly influences its' gravitational pull - its' hill sphere. That's how far away an object can be to be pulled into orbit."
So other objects - moons, asteroids, satellites, etc... can orbit the planets. The *difference* is that the planet has less mass than the sun/star, and it's within the hill sphere of the sun/star.
So the hill sphere of your planet is influenced by the hill sphere of the sun/star. OR, more accurately, by the mass of the sun/star.
We'll ignore eccentricity for a moment, because it makes for unfavorable orbits. Therefore, the method for calculating the hill sphere of any object IN ORBIT around another object with more MASS (like a planet around a sun) is:
"r" (the radius of the hillsphere) is (approximately) equal to "a" (semi-major axis of the sun) times the CUBE ROOT of ["m" (the mass of the planet/object) divided by 3 times "M" (the mass of the star/more massive object).].
When the Mass of the star changes, so does the hill sphere of everything orbiting it.
If the hill sphere of the planet changes, that affects the moons/subsatellites that can orbit it.
So... hotter sun = more mass = larger/stronger hill sphere = smaller PLANETARY hill sphere = different plausible/im-plausible orbits for the moons = different masses/distances for the moons = different hill spheres for the moons = no sub-moon/different conditions for the sub-moon, etc.
So I'd still have to redo all the calculations.
That being said.... It IS a good solution. I probably will be doing that. In fact I'll probably go in increments... star a little hotter, planet a little closer, back and forth until I can find the sweet spot (or rather, heat spot) that will let my people survive. When I asked how to make it hotter, I was hoping for some atmospheric ideas that would save me from re-calculating. Cause math melts my poor little brain.
I wonder if I could commission an astrophysicist on a forum somewhere....
Originally Posted by Azelor
OH I see.
Still, Earth is (149,600,000 km) from the sun. Planet N is (509,679,000 km) from the sun. It's much further away?
(Edit: Nevermind, I see ... I made a mistake in transcribing the "miles"... still it would be too cold, so it doesn't matter.)
A white dwarf might work, it would cool, but not in the lifetime of a universe, so it's conceivable....
YOU GUYS ARE SMART. I'm going to go play with those numbers.
Hm... regarding atmospheric changes, how about a higher concentration of CO2 or methane in the air? Yeah, we think 'global warming' when we hear those two gases, but CO2 at least was around in force during the time of the dinosaurs too, when it was significantly hotter on earth. Perhaps your planet could fairly young (geologically speaking) and still coming up with new volcanoes every twenty minutes.
Yeah, I wonder how hot I could get it without poisoning my people, though... ?
Well, as long as you have an appropriate quantity of oxygen in the atmosphere, your humans could probably adapt to higher CO2 concentrations at least. CO2's actually a critical part of our breathing process - receptors assess the acidity of our blood caused by CO2, which prompts our lungs to inhale when a certain acidity is reached - so maybe your planet's humans could have a higher tolerance to internal acidity? Or even a higher native acidity, with their tissues having a lower pH than earthling tissue does and thus a lower breathe-in-now-please point from the body's acidity receptors.
Yeah... it sounds plausible. Biology isn't my strong point, but I can see how that would work.
It's certainly easier to play with than re-mapping my entire solar system
I'll toy with some numbers and bug people on some science forums and see how much of that I can get away with