The Solar System, Great Lakes Earth

[Jdailey1991]

Compared to the planets we have discovered in the past decade, our solar system seems...ordinary. It was thought that no planet could get any closer to the sun than Mercury, let alone one the size of Jupiter. It was thought that Earth is the largest it could get with the right gravity and atmosphere to harbor life. It was thought that no planet could get any bigger or heavier than Jupiter.

In this scenario, I present to you an alternate solar system. The names listed below are not the actual names that I chose for my alternate universe, but rather the planets that inspired them.

One--55 Cancri E

Diameter--2x that of Earth

Mass--8x that of Earth

Distance from the sun--5.5 million miles

Two--Gliese 581 C

Diameter--1.75x that of Earth

Mass--5.5x that of Earth

Distance from the sun--51.61 million miles

Three--Earth

Three a--"Supermoon"

Diameter--3200 miles

Distance from Earth--+300,000 miles

Mass--1.3452 x 10^23 kilograms

Four--GJ 1214b

Diameter--2.6x that of Earth

Mass--7x that of Earth

Distance from the sun--141.6 million miles (1.5 AU)

Four through Six--Jupiter, Saturn and Uranus. No difference in diameter, mass, or distance from the sun.




Would any of these changes affect orbit dramatically, or not by much?
Would we still have an asteroid belt separating inner from outer planets?
What would the day/night sky look like?
Would these changes alter Earth's Milankovitch cycles in any way?

 

[chaosattractor]

I'm no astrophysicist, but I'm pretty sure you can't just pick and choose bodies from different planetary systems and throw them together around a different star. It would be beyond extreme coincidence for them to form the same way.

So yeah, a heck of a lot is going to change; I'm not qualified to say what exactly. As for the asteroid belt, that was caused by Jupiter's gravity preventing a planet from forming if I recall correctly.

 

[X Equestris]

A lot is going to depend on what sort of star your sun is. A system centered on a red dwarf would be very different from a sun like star, which would be very different from a blue supergiant. So...what is your sun?

 

[Jdailey1991]

A lot is going to depend on what sort of star your sun is. A system centered on a red dwarf would be very different from a sun like star, which would be very different from a blue supergiant. So...what is your sun?

The same as back home. If it were any different, I would've mentioned it.

 

[chaosattractor]

I mean, two of the planets you picked orbit red dwarfs...

 

[Jdailey1991]

I mean, two of the planets you picked orbit red dwarfs...

Back home, maybe.

 

[chaosattractor]

Back home, maybe.

Have you calculated the orbital periods of your planets?

 

[Jdailey1991]

Have you calculated the orbital periods of your planets?

Not relevant at the moment. What I am aiming at is whether these changes will alter Earth's Milankovitch cycles, and if so, to what extent.

 

[chaosattractor]

Not relevant at the moment. What I am aiming at is whether these changes will alter Earth's Milankovitch cycles, and if so, to what extent.

Sorry - you mentioned orbit, I didn't know you meant Earth's orbit in particular. I mentioned orbital periods because iirc you need that to figure out each planet's apparition. How to do that, however, I don't know.

 

[K.S. Crooks]

You should start with the basic physics that are in play in all systems.
The more mass a star has he greater its gravitational effect. The closer a planet is to a star the hotter it becomes, and the faster its orbit. In the main sequence, the hottest stars are blue, then white, yellow orange, red. Stars in various stages of dying have different temperature, colours and masses.
Each star has a "Goldilocks zone", which is the minimum and maximum distance from the star where liquid water can exist. As currently liquid water is the one criteria needed for all life to exist. The planet needs to have enough mass to create a magnetic field to maintain its atmosphere and water/oceans. (The reason Venus and Earth have an atmosphere and Mars doesn't.
A planet's rotation speed determines day and night cycle time. Tilt determines seasonal variations. The mass and distance of any moons will affect tides.
After all of this you can determine what you want for the composition of the atmosphere, how much water vs land, plants and animal life. As we have discovered about our own and other star systems, there can be great variation between planets around the same star. Good luck.

 

[Jdailey1991]

That's...rather broad.

 

[buyjupiter]

Not relevant at the moment. What I am aiming at is whether these changes will alter Earth's Milankovitch cycles, and if so, to what extent.

Yes. Planet mass affects orbit which affects all of the things considered in the Milankovitch cycle. I'd really recommend reading Martin Ree's "Six Little Numbers" to understand more fully how shifting one little thing has vast consequences for everything else that follows. Then apply that logic to your solar system creation. [It's not directly related to the question you're asking but it deals with the forces of the universe which do apply to the question you're asking.]

More important than mass tho is how close to your star each planet is. If we were as close as Venus is, we'd be toasty. If we were as far out as Mars, there's not enough luminosity for plant life to easily form. [Variations in axial tilt and orbital distance from sun don't affect our planet nearly as much as average distance from the sun does. Earth has a natural variance in certain orbital parameters in any case.]

Water does not have to be liquid for life to form, it's just easier when it is. [And it reallllllly depends on if we're talking about a civ that grew up in situ with non-liquid H2O, or a galaxy traversing species who can melt water. Because we just need water. We are advanced enough that we can melt ice or condensate vapor.]

 

[Jdailey1991]

The planet's distance is still 93 million miles from the star. If it were any different, I would have said so.

 

[buyjupiter]

The planet's distance is still 93 million miles from the star. If it were any different, I would have said so.

If the planet's distance from the star is exactly the same, the star's mass/luminosity is exactly the same, then you have Earth. Distance and mass play into each other. So you can't have Earth distance from our sun AND change in mass like the example planets you shared, without having massive changes to other parts of that system. Some of those are going to be axial tilt and climatalogical. Some of those changes are going to be either fewer inner planets or fewer planets clearing their own orbits [and that opens up a whole nother can of worms about defining planets--the minute things stop clearing their own orbit and are about Earth sized it gets iffy on whether or not they are planets].

But if nothing changes from how we currently see our solar system, ie it's "all the same", then you have Earth and I really am not understanding why you'd try to change it...? Also, ANY tiny change to any of the "numbers" and you have wildly different possibilities, so if I were you I'd start mucking about with changing the numbers to get the changes I want. [For example, I'd look into how big I could make a rocky planet without making the gravity so onerous no life could get started and then I'd go to the other extreme and see how light a planet you could have without it losing its own atmosphere, aka Mars.]

 

[Jdailey1991]

If the planet's distance from the star is exactly the same, the star's mass/luminosity is exactly the same, then you have Earth. Distance and mass play into each other. So you can't have Earth distance from our sun AND change in mass like the example planets you shared, without having massive changes to other parts of that system. Some of those are going to be axial tilt and climatalogical. Some of those changes are going to be either fewer inner planets or fewer planets clearing their own orbits [and that opens up a whole nother can of worms about defining planets--the minute things stop clearing their own orbit and are about Earth sized it gets iffy on whether or not they are planets].

Uh...Look back at the question and see that that is the point. It's just to see how having these different planets would affect Earth's Milankovitch cycles.

 

[Ixidor]

Would any of these changes affect orbit dramatically, or not by much?
Would we still have an asteroid belt separating inner from outer planets?

Based off the conversation of the thread, it seems like you're aiming for the hard science side of things. I can't tell you about the physics of any of it, but here's my two cents for whatever it's worth:

Something to keep in mind is that we're operating on limited data here. So far as we know, life is incredibly diverse and can survive in a huge rage of climates. However, the requirements for life are extremely high. This may explain the contradiction between the ton of life we see when it exists, but also the extreme rarity when it comes to the it's overall existence in the entire galaxy.

So ultimately, as far as we know, there's only one exact path to the existence of life on a planet, and that's our solar system down to every variable. Thinking from the perspective of a god: who knows what variables we could change without ruining that chance for life? Take out Jupiter and maybe we get a few too many cataclysmic meteors that hit Earth and make it inviable for life.

That said, if you haven't already, it may not hurt to pick up the Planet Construction Kit by Mark Rosenfelder. He goes into a fair amount of detail on things you may find useful.

 

[Fenrir]

@OP

Interesting. I will throw in my hat for what its worth. Non-degreed here in the subject, so be warned. ;P

1) Would any of these changes affect orbit dramatically, or not by much? <- you have a lot more mass near earth in those planet changes, so I would say yes, for at least a moderate bit.

2) Would we still have an asteroid belt separating inner from outer planets? <- Maybe, jury is still in debate as to how that got there afaik. Napkin math says I would lean to "yes" - if we go with the Jupiter killed a forming planet theory. That is, the new Mars is more massive so would be adding even more 'tug of war' onto that forming body. Final orbit might be somewhat closer in tho as the new 'mars' is more massive.

3) What would the day/night sky look like? -> Well bigger planets near Earth would give bigger 'morning star' type effects. Probably would play out in mythology as those bodies being more prominent 'Greek gods' and such. Beyond that unless you have your new bodies with a darn high albedo I think that would be about it.

4) Would these changes alter Earth's Milankovitch cycles in any way? -> Sure. Orbit changes due to other bodies would no doubt causes changes. I mean Earth might be tilted more, have a more eccentric orbit, or orbit more offset from 'the ring' like say... Pluto. No way I could tell you what would happen. But, happen it probably would. Maybe poke some astronomy/astrophysics forums?

5) Could the first planet that large actually be that close to a mid range star such as the sun? Not one of your questions, but darn that sucker is like right next door in solar system terms how you have it. Even if it was a captured wanderer I would think the sun would gravitationally work over that bad boy like a dog's chew toy.

@K.S.

I am with you on gravity mostly. But pretty sure gravity is what traps atmosphere. Magnetism is what provides a shield versus radiation. While related, they could vary. Such as a large, but not so dense planet, having enough gravity to trap atmosphere but potentially having a weak enough magnetic field so that say... land life would get DNA fried if it were to close to its star(s).

There are scenarios that you could change Goldilocks zones if desired. Close in planet shielding a large locked moon. Large Jupiter+ like planet actually being brown dwarf which would change things in system. Or, even a very high Albedo Jupiter like reflecting more light onto moons. Subsurface water. Etc.

 

[Jdailey1991]

Maybe poke some astronomy/astrophysics forums?

Know any that allow what-if questions?

 

[Fenrir]

Know any that allow what-if questions?

Google fu finds this

Astronomy and Astrophysics | Physics Forums - The Fusion of Science and Community

Seem to be what if questions posted there. I do not doubt there are others.

 

[Jdailey1991]

Google fu finds this

Astronomy and Astrophysics | Physics Forums - The Fusion of Science and Community

Seem to be what if questions posted there. I do not doubt there are others.

I got in trouble from Physics for posting such things.