The Grand Planet Formation Discussion Thread!

[RA3236]

So, while @SAS123 and I were engaged in a PM thing about the orbits of Jupiter and the other planets (which was really informative, thank you) I thought of a good topic to discuss. Put anything related to planet for,action here!!!

[SAS123]

If anyone also wants to know, I'll see if i can explain the Kerbol Solar System Formation

 

Edited April 26, 2016 by SAS123

[RA3236]

5 minutes ago, SAS123 said:

If anyone also wants to know, I'll see if i can explain the Kerbol Solar System Formation

 

Please do so  

[Wjolcz]

Ya can't! NovaSilisko, who is the one who created it, proved that the Kerbolar (who even came up with this name?) system would be sort of unstable. Mainly the Jool system had some problems keeping the moons in the same orbit. Also Minmus had some problems and Gilly would need a third body to be captured IIRC.

[SAS123]

15 minutes ago, Veeltch said:

Ya can't! NovaSilisko, who is the one who created it, proved that the Kerbolar (who even came up with this name?) system would be sort of unstable. Mainly the Jool system had some problems keeping the moons in the same orbit. Also Minmus had some problems and Gilly would need a third body to be captured IIRC.

I don't care. It isn't real life. haha. Yea in real life Kerbol couldn't Exist because of its size and Temperature would cause itself to rip apart. Jool would also disband unless its absolutely tiny core is as massive and dense as Earth because of its thick atmosphere, it would turn into most likely a Chthonian planet. With its small mass as well the moons would be unstable and its possible Laythe would turn into a semi-Icy Ring system. Minmus might melt into a Icy Dust ring around Kerbin. Eve's Moon if we hypotheticalise could have been there for a long time if two kerbin sized planets smashed into each other and colilsed back into a large planet like it is now but Gilly is a renament of that collision and Ksp just kept it a secret.

But I'm still thinking of how it would have formed.

Edited April 26, 2016 by SAS123

[kerbiloid]

Unless the gravitational constant differs from 6.67e-11 here.

[PB666]

1 hour ago, SAS123 said:

I don't care. It isn't real life. haha. Yea in real life Kerbol couldn't Exist because of its size and Temperature would cause itself to rip apart. Jool would also disband unless its absolutely tiny core is as massive and dense as Earth because of its thick atmosphere, it would turn into most likely a Chthonian planet. With its small mass as well the moons would be unstable and its possible Laythe would turn into a semi-Icy Ring system. Minmus might melt into a Icy Dust ring around Kerbin. Eve's Moon if we hypotheticalise could have been there for a long time if two kerbin sized planets smashed into each other and colilsed back into a large planet like it is now but Gilly is a renament of that collision and Ksp just kept it a secret.

But I'm still thinking of how it would have formed.

I have the answer, change the fine structure constant. 

 

[kerbiloid]

1 hour ago, kerbiloid said:

Unless the gravitational constant differs from 6.67e-11 here.

 

16 minutes ago, PB666 said:

change the fine structure constant. 

http://www.scp-wiki.net/scp-536

[sevenperforce]

I had assumed that this would be a thread about terrestrial planet formation as opposed to other types of formation from protoplanetary disks.

I am also quite thrilled that my phone's voice text has the ability to understand the word protoplanetary.

Back on topic: hypothetically, would it be possible for a trinary star system to form in such a way that one of the planets is continually bathed in sunlight, resulting in eternal day?

 

[Bill Phil]

2 hours ago, kerbiloid said:

Unless the gravitational constant differs from 6.67e-11 here.

Nope. It's the same. It has to be. The masses given and the surface gravities and the orbital velocities wouldn't be what they are.

30 minutes ago, sevenperforce said:

I had assumed that this would be a thread about terrestrial planet formation as opposed to other types of formation from protoplanetary disks.

I am also quite thrilled that my phone's voice text has the ability to understand the word protoplanetary.

Back on topic: hypothetically, would it be possible for a trinary star system to form in such a way that one of the planets is continually bathed in sunlight, resulting in eternal day?

 

Possibly. Unlikely, though. 

There are mountain peaks on the moon with almost eternal light.

[Gaarst]

32 minutes ago, sevenperforce said:

Back on topic: hypothetically, would it be possible for a trinary star system to form in such a way that one of the planets is continually bathed in sunlight, resulting in eternal day?

Trinary stars systems can form, and I'm pretty sure there are a lot forming out there. Stability is another thing, trinary star systems are very unstable, and if one star doesn't get thrown off in a few million years, you can bet that any planets that could have formed would.

Eternal day would mean that the planet would sit somewhere in between the three stars, a place you don't want to be, and in which anyway, you won't sit for long before your planet gets thrown into interstellar space ridiculously fast.

Tidal locking can give you eternal day, but on half the planet only.

[adsii1970]

6 minutes ago, Gaarst said:

Trinary stars systems can form, and I'm pretty sure there are a lot forming out there. Stability is another thing, trinary star systems are very unstable, and if one star doesn't get thrown off in a few million years, you can bet that any planets that could have formed would.

Eternal day would mean that the planet would sit somewhere in between the three stars, a place you don't want to be, and in which anyway, you won't sit for long before your planet gets thrown into interstellar space ridiculously fast.

Tidal locking can give you eternal day, but on half the planet only.

Unless - and there is another option, but it would only bathe the plant in complete light for a fraction of the year... If you take Earth's solar system (for reference only) and where our sun is, simply add a second star at the orbit the earth has (and move the rest of the solar system further out and make orbits nearly oval-like), then have a smaller star, say a brown dwarf or red dwarf, out in the Kuiper belt range, it might work - at least it did in Universe Sandbox

Anyhow, I ran the simulation, accelerated for about an hour; the orbits of planets do shift over time to accommodate the two stars at the center, more elliptical orbits manifest themselves, and nearly every asteroid is flung out of the system. It was pretty wild to watch...

[kerbiloid]

43 minutes ago, Bill Phil said:

The masses given and the surface gravities and the orbital velocities wouldn't be what they are.

Planet radius, gravity and orbital velocity are given and directly measurable.
The planet masses are just presumed on the 6.67e-11 assumption.

By radius and gravity we can get GM, not G or M.

P.S.
I had already noted a book which I'm fond of: Raft.

 

Edited April 26, 2016 by kerbiloid

[sevenperforce]

20 minutes ago, adsii1970 said:

Unless - and there is another option, but it would only bathe the plant in complete light for a fraction of the year... If you take Earth's solar system (for reference only) and where our sun is, simply add a second star at the orbit the earth has (and move the rest of the solar system further out and make orbits nearly oval-like), then have a smaller star, say a brown dwarf or red dwarf, out in the Kuiper belt range, it might work - at least it did in Universe Sandbox

Anyhow, I ran the simulation, accelerated for about an hour; the orbits of planets do shift over time to accommodate the two stars at the center, more elliptical orbits manifest themselves, and nearly every asteroid is flung out of the system. It was pretty wild to watch...

Sounds awesome.

There are a couple options I thought of. One is a trojan arrangement, where you have a large primary and a small secondary (hot brown dwarf, maybe) and the planet is at one of the trojan points of the secondary. Not sure where the third star could go to supply the other required illumination, though.

Also possible to have a multiplanar arrangement, with the primary and secondary in a fairly tight binary and a third star in a highly elliptical orbit perpendicular to the ecliptic, but where the third star has forced an orbital resonance with the planet so that their orbits always coincide without disruption.

[CSE]

Agreed, I think a trojan of a brown dwarf or highly-reflective planet would be the best bet. The Earth night under a full moon is bright enough for daytime creatures like humans to find their way around if not dazzled by other light sources. I imagine that the lunar night under even a first/last quarter Earth is functionally 'daytime' for many purposes.

In addition, the period of daylight on Earth is normally longer than the technical solar day, owing to atmospheric refraction. I wonder how refractive an atmosphere can get?

[sevenperforce]

21 minutes ago, CSE said:

Agreed, I think a trojan of a brown dwarf or highly-reflective planet would be the best bet. The Earth night under a full moon is bright enough for daytime creatures like humans to find their way around if not dazzled by other light sources. I imagine that the lunar night under even a first/last quarter Earth is functionally 'daytime' for many purposes.

In addition, the period of daylight on Earth is normally longer than the technical solar day, owing to atmospheric refraction. I wonder how refractive an atmosphere can get?

High-density atmosphere for refraction...I like it.

If any of you don't know, the idea originally came from Namek in the DBZ series, where it is supposedly always daytime everywhere on the planet, and the planet has three suns (though only one or two are ever simultaneously visible, of course).

Consider a binary between a sun-like star and a brown dwarf, where the brown dwarf has a high-albedo ice/water giant and a small terrestrial planet in moderately eccentric orbits. The sun-like star forces the argument of periapse for the two planets, which are in resonance so that the ice giant is at its apsis on the far side of the brown dwarf whenever the terrestrial planet is at its periapse on the far side of the planet.

[Shpaget]

 

Somewhat old, but should still be relevant.

[SAS123]

8 hours ago, sevenperforce said:

I had assumed that this would be a thread about terrestrial planet formation as opposed to other types of formation from protoplanetary disks.

I am also quite thrilled that my phone's voice text has the ability to understand the word protoplanetary.

Back on topic: hypothetically, would it be possible for a trinary star system to form in such a way that one of the planets is continually bathed in sunlight, resulting in eternal day?

 

I could see eternal day of a planet in a binary system but I'm trying to place a flat surface planet in my head in a trinary star system so all three stars are lighting it up but I can't find a spot where it would never be dark at all. And for the binary part the only place I can think of is between both stars exactly where the center of mass is for both stars or otherwise the planet would have to orbit around one star as fast as the other star orbits around the planet star.

[Darnok]

21 minutes ago, Shpaget said:

 

Somewhat old, but should still be relevant.

What software you are using?

[CSE]

45 minutes ago, SAS123 said:

otherwise the planet would have to orbit around one star as fast as the other star orbits around the planet star.

If I've parsed that correctly, that's another way of describing the L1 Lagrange point.

The L4 and L5 trojan points are located in stable regions for a satellite to orbit, if not disturbed by other massive bodies. Lagrange points L1, L2, and L3 are not stable in this way and even a very small disturbance tends to push the bodies at those points out of their orbits.

Edited April 26, 2016 by CSE
(pic inserted properly)

[sevenperforce]

3 minutes ago, SAS123 said:

I could see eternal day of a planet in a binary system but I'm trying to place a flat surface planet in my head in a trinary star system so all three stars are lighting it up but I can't find a spot where it would never be dark at all. And for the binary part the only place I can think of is between both stars exactly where the center of mass is for both stars or otherwise the planet would have to orbit around one star as fast as the other star orbits around the planet star.

Yeah, a binary system allows for temporary full illumination, but you need a third or fourth star to get permanent complete illumination. You would definitely need to have an eccentric orbit somewhere. But if you have a nice 1:1 or 2:1 resonance going on, then you should be able to ensure full coverage.

Let our sun be the first star, let earth be the second star, let our moon be the third star, and let a test mass orbiting earth represent the target planet. Place the test mass in an eccentric orbit with the apogee at 3x the Earth-moon distance and the perigee at roughly 2/3rds the Earth-moon distance, such that it has an orbital period of two months. If the semimajor axis points toward the Sun, such that the apogee is the nearest approach to the Sun, then the moon will complete two orbits for every one orbit of the test mass, always lining up at opposition precisely when the test mass is at apogee and opposition. 

If the primary is large and distant enough, then the resonant orbits will be kept in alignment with the primary because their period is so much lower. This is easier if the two tighter orbits are retrograde. Plus, if the masses and luminosities of the stars are correct, average insolation should remain roughly constant...perhaps with slight global seasons. The sizes, positions, and apparent brightness of the suns would change over time but not dramatically. 

Another question on planet formation inspired by DBZ: what's the highest surface gravity a naturally-formed terrestrial world could have? Assume it must still have a breathable atmosphere. 

[SAS123]

5 minutes ago, sevenperforce said:

Yeah, a binary system allows for temporary full illumination, but you need a third or fourth star to get permanent complete illumination. You would definitely need to have an eccentric orbit somewhere. But if you have a nice 1:1 or 2:1 resonance going on, then you should be able to ensure full coverage.

Let our sun be the first star, let earth be the second star, let our moon be the third star, and let a test mass orbiting earth represent the target planet. Place the test mass in an eccentric orbit with the apogee at 3x the Earth-moon distance and the perigee at roughly 2/3rds the Earth-moon distance, such that it has an orbital period of two months. If the semimajor axis points toward the Sun, such that the apogee is the nearest approach to the Sun, then the moon will complete two orbits for every one orbit of the test mass, always lining up at opposition precisely when the test mass is at apogee and opposition. 

If the primary is large and distant enough, then the resonant orbits will be kept in alignment with the primary because their period is so much lower. This is easier if the two tighter orbits are retrograde. Plus, if the masses and luminosities of the stars are correct, average insolation should remain roughly constant...perhaps with slight global seasons. The sizes, positions, and apparent brightness of the suns would change over time but not dramatically. 

Another question on planet formation inspired by DBZ: what's the highest surface gravity a naturally-formed terrestrial world could have? Assume it must still have a breathable atmosphere. 

There have been super-earths about 8 x the mass of earth that are rocky with maybe not breathable(because oxygen is generated by plants) but about twice the thickness of earths. But Planet 9 is estimated to be 10 earth masses and its supposably an ice giant.

[cubinator]

11 hours ago, Veeltch said:

Gilly would need a third body to be captured IIRC.

Eve has a lot of impact craters, especially considering it's dense atmosphere and oceans. There could very well have been such a body a geologically short time ago, which later impacted Eve. Minmus could have been captured in a similar situation, and there is a giant impact crater on Kerbin as well.

But yes, Kerbol's density causes it to be a black hole in Universe Sandbox.

Edited April 26, 2016 by cubinator

[sevenperforce]

12 minutes ago, SAS123 said:

There have been super-earths about 8 x the mass of earth that are rocky with maybe not breathable(because oxygen is generated by plants) but about twice the thickness of earths. But Planet 9 is estimated to be 10 earth masses and its supposably an ice giant.

Eight times more massive with twice the radius is merely 2 gees.

Would probably be fractionally higher because it would necessarily end up denser than Earth.

Ought to still be able to support plant life, in theory. Different atmospheric makeup for sure...going to retain a lot more gas so it will be unlikely to have an atmospheric pressure anywhere near earth's at the surface. Though that's not necessarily a problem. 

Edited April 26, 2016 by sevenperforce

[More Boosters]

1 hour ago, sevenperforce said:

Eight times more massive with twice the radius is merely 2 gees.

Would probably be fractionally higher because it would necessarily end up denser than Earth.

Ought to still be able to support plant life, in theory. Different atmospheric makeup for sure...going to retain a lot more gas so it will be unlikely to have an atmospheric pressure anywhere near earth's at the surface. Though that's not necessarily a problem. 

 

Just imagine the disappointment when an intelligent race emerges in such a planet, gets sufficiently advanced and then calculates the Delta-V requirements for pushing through their thicker atmosphere and 2g.