@Epsilon Tauri
I will try to provide good responses to your statements, I really appreciate the interest. Do be known, that this is an alternative history timeline, which I am not going into, until it is posted by the person who covered the map and lore of it. I requested all this information, and the majority of the lore behind it, I just had someone compile it and map out the alternative history portion of it. You won't be seeing this on a map, but hopefully what you see will be interesting enough.
We're doing Mars sample returns by the early 2000s? That's great!
How do we discover the lakes under the ice caps?
I would imagine the lakes discovered under the ice caps are done by orbital probes scanning the poles. I do not know much about this, but, I would assume that it would be something we would be capable of knowing. Best guess I can give for what the life on Mars would be like - think about under the ice of Antarctica.
Are you sure you don't mean a dwarf planet, or is the IAU definition of a planet different ITTL? The asteroid belt does still exist, so it hasn't cleared its orbit.
It is different. Any object that is gravitationally round by it's own gravity is considered a planet in this timeline (think Pluto, Ceres, Eris, Sedna, etc, added to the planet list) I have always very much disagreed with the IAU standards. I will not accept the idea of Dwarf Planets not being considered planets. Personal bias and subjectivity, I know, but, it's the way I see these things.
Sure, that's not far off from reality anyway
There even exists possible evidence of it in this timeline, as far as I know. In this timeline, the Moon Rhea's rings are quite prominent. They are not small arcs like the rings of Neptune. They are a relatively solid, and visible ring system like that of Saturn's, but on a far smaller scale, of course. Existing well within Rhea's sphere of influence, their prominence would indicate they formed in the past few million years or so, so are relatively young in the scheme of the solar system.
https://en.wikipedia.org/wiki/Rings_of_Rhea
So Titan is scaled up by ~4.5x and life-infused, but otherwise similar to OTL. Doesn't sound too unreasonable. Since methane and ethane are non-polar, the chemistry of this life must be very different from Earth; I don't know very much about this, but I'm sure it would be fascinating to flesh out.
I do not know exactly how this life would look. I have been imagining Fractal like structures, like plants, almost. Living crystals, so to speak. Perhaps they would take thousands of years to fully mature, if conditions get right. Titan does not have intelligent life. Animal life would likely be small, and focus on conserving energy. Perhaps organisms that blurr the lines between plants and animals. Titan is very cold. Life must conserve energy and heat. By not moving. Perhaps the skies of Titan are filled with small floating plant-like creatures that have a life cycle up in the sky as the wind currents carry them about.
Unlike the Titan of our world, it's liquid lakes and oceans are not confined to the Equator. I would imagine roughly 60% land and 40% ocean.
This Titan, as it is much larger than our Titan - I'll say the outer Moons of Saturn are different. Titan orbits where it sits currently, while Hyperion and Iapetus exist further out from Saturn. How much further out, and how their orbits would differ - I don't know. Stable orbits, with Hyperion existing in a resonance with it.
Something else has crossed my mind about Hyperion. Maybe Hyperion could be a smaller version of Titan, roughly the mass of our Moon. Imagine the two Moons with similar biospheres via panspermia? Just a proposal, not sure how realistic that would be.
That orbit gives it a period of ~6550 years. Where in its orbit is it currently? Nearer to perihelion or aphelion? Is it close to ascending or descending node, or is it currently far out of the ecliptic?
What ices is it made of? What's the radius? About 2.6 times Earth's is my estimate, given icy composition and mass.
I do not know about that. It's orbital period means, at least in my eyes, it would not affect the orbits of the other planets or Kuiper belt. Minthe, in mind, as a large super-terran iceworld - it has a fairly cratered appearance. Minthe exists in such a cold region of the solar system, that I can imagine it has a thin atmosphere. Minthe's atmosphere does not sublimate, like that of Pluto. It is simply too far away for it's atmosphere to change that much. Good luck landing on Minthe. There won't be that much of an atmosphere to slow you down.
Minthe, likely does have a global ocean underneath it's surface. Far more expansive than that of any ocean elsewhere in the solar system. Tons, and tons more water than that is on the Earth. By how much, I don't know.
No kidding - Voyager 1 launched half a century ago and is only 160 AU away, and this is more than twice that!
Best I could think would be sending lightsail probes out to do a fly by of it, but even then, we may not see pictures of it up close within our lifetime.
When you say "similar in size", do you mean mass or radius? I assume all of these moons are icy as well.
Based on
this spreadsheet, Nox would have an absolute magnitude of almost 27 - close to the limit of what our telescopes could probably find.
Similar in Mass. If you are saying that Nox is the only one that would be large enough to be visible, I do not know about that. I do not know anything about orbital mechanics or how visible these sorts of things would be in space, that's for someone with more talent and knowledge than I to figure out.
I think Nox is a good estimate for the minimum resolvable size. Do Minthe's moons orbit in the same plane as it?
Yes they do. I imagine Minthe's main moons are similar in composition to that of Kuiper belt objects. All icy, with the major ones being cryovolcanic like Enceladus. I am also imagining that because of Minthe's lack of a substantial atmosphere, the rings themselves extend fairly close down to the planet. I would imagine that the record of "Moon with a shortest orbital period around a planet" would be one of Minthe's inner minor moons, likely a small moon similar to that of the moons of Saturn that inhabit it's rings. Going around the planet in mere hours.
You say seven planets, but I think you only list four. A typical M7V star has a luminosity around 6.5 * 10^-4 Lsol.
There should have been 5, but you are right, I only listed four. The main 4 I listed are the names that matter. Perhaps I can think of more planets for Nemesis, but I am not sure what else to add to it. What magnitude would Nemesis be?
Have most of our observations been with transits then? Do the planets transit?
Perhaps they would. We can say that the orbital plane of the Nemesis system is tilted so transits are able to be observed like around other stars.
This orbital period with this star gives about 0.00990 AU for orbital radius.
My intentions for the first planet is for it to be a hothouse world similar to Venus. Intense atmospheric pressure. Intense heat. Thick atmosphere. Likely hotter than Venus, possibly.
The distance to the star would be 0.0280 AU. How did we confirm water? Spectra? The planet is too small and close to its star to resolve. I really like this idea. Do we know if the liquid water is exclusively on the terminator? What's the temperature differential like?
I would propose that this planet is in a 2:3 resonance, so for every 2 times it orbits, it rotates 3 times. But I do not know if this is possible. If it's not, then we'd have a terminator line where liquid water is present.
30. days -> 0.0847 AU
This is a fun concept. The gravity, mass, and radius more or less check out; Venus radius and 0.5 earth mass gives 0.55 g, while 0.5 earth mass and 0.625 g gives 0.94 Venus radius.
0.5 Earth mass, but similar in radius to Venus, yes.
If these planets were discovered with transits - how long have we been watching Nemesis, to have confirmed a 21-year period? If it's some other method, which? They don't appear to have a resonance, which somewhat surprises me given how close in they orbit.
I simply put that "21 years" in since I didn't know what else to put. I wanted to have a resonance, but I do not have the manners to calculate that. Perhaps you could help me with these planets, and we can create a solid groundwork for the Nemesis system, you seem to know more than me.