@Epsilon Tauri
I wouldn't put it past the chance of possibility that Prosperina could even have it's own captured Moons, despite being a moon. The vast distance from Minthe would make it possible. I would suggest for Prosperina to have a relatively fast rotation period (perhaps 9-10 hours), being indicative of an ancient collision in the past, with many of Minthe's outer moons being material that once belonged to Prosperina and whatever large impactor hit it, and around Minthe, some of Prosperina's orbital moons could be co-orbital bodies, much like Jupiter Trojans.
I am thinking it makes sense for it to be tidally locked. Since these planets are so close to the star, they would have close to zero eccentricity, indeed. My idea is that Acheron is the habitable, Earth like planet of the system. It may have life, but, I am not sure what kind of life would be there.
Adjusting the planets to that configuration is also possible. Is it possible that more planets could exist within this system? I could think of some more additions for this system. I would propose them here, and let's see what you think, while listing already existing ones:
Phlegethon is the first planet around Nemesis. It is 0.81 Earth Masses. Observations of the planet have confirmed that it likely has a thick Venus like atmosphere, making the planet similar to Venus. Due to close proximity to Nemesis, it is likely much hotter than Venus is. It orbits Nemesis every 1.2 Earth days. It is tidally locked. The planet is not within the habitable zone as its expected irradiation is more than 4 times that of Earth.
Acheron is the second planet around Nemesis. It is 1.04 Earth Masses. Observations of the planet confirm that it is in the habitable zone around Nemesis and is host to liquid water. It orbits Nemesis every 6.0 days. Compared to other exoplanets around other stars, Acheron is the most Earth-Like exoplanet currently known by mankind. It is not currently known if the planet is host to life by humans. The planet is also tidally locked.
-- These 3 planets could possibly exist between Acheron and Cocytus--
Cerberus is the third planet around Nemesis. It is 0.203 Earth Masses. Poorer in iron, richer in water ice than in our Mars. Cerberus looks like a combination of Mars and Europa: feathery cirrus clouds float above rusty cracked ice-covered seas. Likely an atmosphere of 0.4 Earth Atmospheres. More than Mars, but less than Earth. Enough to form thin wispy clouds in it's reddish skies.
Minos is the fourth planet around Nemesis. It is 0.126 Earth Masses. Similar to Cerberus, this world is host to a Martian-thickness atmosphere and is quite cold. More icey than Cerberus is, though. It is very similar to our Mars, although it is more of an iceworld than Mars is.
Rhadamanthus is the fifth planet around Nemesis. At 2.9 Earth Masses, despite Rhadamanthus's rather Jovian appearance, it's a water world. It's dense atmosphere is rich in ammonia and water vapor that hides deep worldwide oceans, down to where atmospheric pressures are high enough to trap heat. It may very well have life down in those dark seas. Complex life may be sparse - if not entirely absent. Possibly gaining energy from the flashes from the constant lightning in it's inner depths?
--
Cocytus is a low density world as big as Venus but just 0.5 Earth mass and 5/8 Earth's gravity. It's like a much bigger Titan on a balmy interglacial day: warmer and wetter, 'wetter'. If you could call gasoline wet, that is. Air pressure at sea level is 4 atmospheres. It's atmosphere is mostly hazy with hydrocarbons evaporating off of ethane seas. Rain won't be a rarity, as on Titan in OTL. If life is found to exist here, it may exist in similar forms to Titan's life. Life here would likely still be evolving very slowly, thanks to how cold the planet is. Cocytus goes around Nemesis every 30 days.
Hecate is an 2.1 Earthmass Ice World, existing at an orbital distance of around 150(?) days. A frozen, bleak world marked by it's airless nature - it would be otherwise unusual. If not, thanks to it's high rate of rotation. Rotating every 9 hours or so, the planet has had no major moons to slow it's day length down, and it exists outside of the tidal-locking zone of Nemesis. Perhaps it's rotation rate may have been caused by an impactor in it's past, if the large population of asteroids just past it's orbit is any indication. None of them stuck around in Hecate's sphere of influence to create any moons, though.
The final planet of Nemesis discovered to date is Lethe. A large mini-Neptune about 5.2 Earth masses. Not much is known about it other than that it exists, and takes 21 years to go around Nemesis. It exists within darkness with both the Sun and Nemesis respectively as the brightest objects in the skies of those planets.
Yes, this makes sense. I do not know the orbital periods of these moons. I am guessing that they orbit in such a way that Persephone - Mors exist all together in a space about the size of Earth-Moon radii. This seems like a large enough area of space for bodies of that mass to settle comfortably within. Prosperina would be likely much further out, perhaps 9 times the distance of the Earth and Moon. This would mean that Prosperina would not be tidally locked to Minthe. Due to Minthe's huge gravitational sphere of influence, it may have hundreds of captured moons ranging in sizes from mere mountains (~1km or so), all the way up to Ceres mass moons orbiting on distant, eccentric orbits.I mean that, as the smallest of them, Nox would still just be visible; the Pluto- and Eris-sized moons, being bigger than Nox, could probably also be detected, and Prosperina would be even easier. However, I think it's right to not include any moons smaller than Nox, because below that threshold they would become harder to detect.
I wouldn't put it past the chance of possibility that Prosperina could even have it's own captured Moons, despite being a moon. The vast distance from Minthe would make it possible. I would suggest for Prosperina to have a relatively fast rotation period (perhaps 9-10 hours), being indicative of an ancient collision in the past, with many of Minthe's outer moons being material that once belonged to Prosperina and whatever large impactor hit it, and around Minthe, some of Prosperina's orbital moons could be co-orbital bodies, much like Jupiter Trojans.
That would make sense. There could be multiple small minor moons orbiting within the period of 3 hours to 10 hours, for extremely close moons. Very small moons though, hundreds of meters, to less than a KM in size. With various small rings of material between them, as the inner shepards they are.Sounds reasonable. A minor moon orbiting within a few hundred km of the surface (working with my estimate of 2.6 R⊕) would have an orbital period of 2 hours 21 minutes.
This makes sense. Nemesis, being a naked-eye star would be an "Average" star in the sky. Nobody would really think anything of it until more modern observations. I would propose that Nemesis has a similar mass to Teegarden's star as well. I am curious about how the Oort cloud would be. Would the Oort Cloud exist around both the Sun and Nemesis (since it is around 1ly out, and Nemesis is at 5,000 AU?) Would Sedna and other such bodies exist, with Nemesis also being there?Given the luminosity value, WolframAlpha says it would have absolute bolometric magnitude (i.e. the entire spectrum, including infrared) of 12.7, and apparent bolometric magnitude of around -0.4. To convert this to visual magnitude, I'll assume, as you said, Nemesis is similar to Teegarden's star - its visual magnitude is about 5 more than bolometric magnitude. This gives an apparent visual magnitude (i.e. visible light) of +4.6, which makes it a naked-eye star, although not a very prominent one, and I think it would be reasonable to not have it be discovered until the early modern era.
I imagine Lethe would have been the last planet discovered. If it takes 21 years, I think one transit wouldn't have been enough to "confirm", so we would need multiple to say for certain it was there.Ok. So we observe Lethe transiting every 21 years? When did we discover it? Is that why we know so little, because we've had so few opportunities to observe it? When was Lethe's most recent transit?
Do all 4 (5?) of the planets transit?
Oh, like Mercury! Interesting idea. I don't know much about Mercury's spin-orbit resonance, but I think that it has to do with its high orbital eccentricity. I don't know if this planet would be very stable with high eccentricity; my instinct is that a planet this close to its star should have almost zero eccentricity, but GJ667C has a planet nearly as close as this with eccentricity around 0.1. Apparently, it's not unreasonable to have a 3:2 spin : orbit resonance there.
This would be possible, it seems, but if you do want the 3:2 resonance, then the orbit should be eccentric, which probably means Cocytus should have an eccentric orbit as well for stability. If that's too complicated or not what you're going for, you could either (a) ignore the lack of realism and do whatever you want (always a fun choice, and you're making this up anyway) or (b) just make it tidally locked.
I am thinking it makes sense for it to be tidally locked. Since these planets are so close to the star, they would have close to zero eccentricity, indeed. My idea is that Acheron is the habitable, Earth like planet of the system. It may have life, but, I am not sure what kind of life would be there.
We have our innermost two planets with 1.2 and 5.7-day orbits. This is very close to 5:1; if we change the outermost orbit to 6.0 days, then 6.0/1.2 = 5, then we get a 5:1 mean motion resonance. This adjustment to the orbital period of Acheron also happens to set up another 5:1 resonance with Cocytus. Then, the overall resonance would be 25:5:1.
Generally, mean motion resonances are as simple as that; just deciding on a ratio of small whole numbers, and then adjusting your orbital periods to match.
Adjusting the planets to that configuration is also possible. Is it possible that more planets could exist within this system? I could think of some more additions for this system. I would propose them here, and let's see what you think, while listing already existing ones:
Phlegethon is the first planet around Nemesis. It is 0.81 Earth Masses. Observations of the planet have confirmed that it likely has a thick Venus like atmosphere, making the planet similar to Venus. Due to close proximity to Nemesis, it is likely much hotter than Venus is. It orbits Nemesis every 1.2 Earth days. It is tidally locked. The planet is not within the habitable zone as its expected irradiation is more than 4 times that of Earth.
Acheron is the second planet around Nemesis. It is 1.04 Earth Masses. Observations of the planet confirm that it is in the habitable zone around Nemesis and is host to liquid water. It orbits Nemesis every 6.0 days. Compared to other exoplanets around other stars, Acheron is the most Earth-Like exoplanet currently known by mankind. It is not currently known if the planet is host to life by humans. The planet is also tidally locked.
-- These 3 planets could possibly exist between Acheron and Cocytus--
Cerberus is the third planet around Nemesis. It is 0.203 Earth Masses. Poorer in iron, richer in water ice than in our Mars. Cerberus looks like a combination of Mars and Europa: feathery cirrus clouds float above rusty cracked ice-covered seas. Likely an atmosphere of 0.4 Earth Atmospheres. More than Mars, but less than Earth. Enough to form thin wispy clouds in it's reddish skies.
Minos is the fourth planet around Nemesis. It is 0.126 Earth Masses. Similar to Cerberus, this world is host to a Martian-thickness atmosphere and is quite cold. More icey than Cerberus is, though. It is very similar to our Mars, although it is more of an iceworld than Mars is.
Rhadamanthus is the fifth planet around Nemesis. At 2.9 Earth Masses, despite Rhadamanthus's rather Jovian appearance, it's a water world. It's dense atmosphere is rich in ammonia and water vapor that hides deep worldwide oceans, down to where atmospheric pressures are high enough to trap heat. It may very well have life down in those dark seas. Complex life may be sparse - if not entirely absent. Possibly gaining energy from the flashes from the constant lightning in it's inner depths?
--
Cocytus is a low density world as big as Venus but just 0.5 Earth mass and 5/8 Earth's gravity. It's like a much bigger Titan on a balmy interglacial day: warmer and wetter, 'wetter'. If you could call gasoline wet, that is. Air pressure at sea level is 4 atmospheres. It's atmosphere is mostly hazy with hydrocarbons evaporating off of ethane seas. Rain won't be a rarity, as on Titan in OTL. If life is found to exist here, it may exist in similar forms to Titan's life. Life here would likely still be evolving very slowly, thanks to how cold the planet is. Cocytus goes around Nemesis every 30 days.
Hecate is an 2.1 Earthmass Ice World, existing at an orbital distance of around 150(?) days. A frozen, bleak world marked by it's airless nature - it would be otherwise unusual. If not, thanks to it's high rate of rotation. Rotating every 9 hours or so, the planet has had no major moons to slow it's day length down, and it exists outside of the tidal-locking zone of Nemesis. Perhaps it's rotation rate may have been caused by an impactor in it's past, if the large population of asteroids just past it's orbit is any indication. None of them stuck around in Hecate's sphere of influence to create any moons, though.
The final planet of Nemesis discovered to date is Lethe. A large mini-Neptune about 5.2 Earth masses. Not much is known about it other than that it exists, and takes 21 years to go around Nemesis. It exists within darkness with both the Sun and Nemesis respectively as the brightest objects in the skies of those planets.