Alternate Planets, Suns, Stars, and Solar Systems Thread

[Epsilon Tauri]

Somewhere in this hypothetical universe is a galaxy made not naturally but through artificial means, with a diameter of 16 million parsecs. This "Z-Kardashev Galaxy" is comprised solely of copies of one same solar system: a single Kardashev-type star with a diameter of 1,860,000 miles and a temperature of 72,000,000,000,000 degrees Fahrenheit, which results in a luminosity of 2,657,599,202,344,462,135,749,473,441,629,625,102,087,912,417 times brighter than the sun. In spite of its massively hyper-high heat, the Kardashev-type star is actually inactive, meaning the heat is trapped within it and can't escape.

I don't really understand how this is supposed to work, on any level. Why doesn't the heat radiate out like it normally would?

Theoretically, it will expand the giant star's lifespan to 100 billion billion years (no, this is not a typo.)

That temperature is equivalent to 4.0 * 10^13 K. At that temperature, hadrons separate out into individual quarks and matter stops acting normal. I don't really understand quantum chromodynamics very well, but my instinct is that if a star gets that hot, it's going to stop being a star. I think this star has more heat than its relativistic mass-energy equivalent, which is hard to wrap my head around. While I will continue to use this value for temperature and the other values you've provided, I would suggest that you decrease the temperature by a large amount, so that you're not causing the laws of physics to break down.
With that luminosity, I think that this star would be brighter than our entire observable universe. That diameter is a little over twice the Sun's. This type of star is physically impossible and its existence would break the universe in a lot of ways. The peak wavelength for electromagnetic radiation from a black body at this temperature is almost at very-high-energy gamma ray levels, and it's well into the spectrum for gamma radiation, at 7 * 10^-17 m.
Based on a simple inverse square law calculation, to receive as much insolation from this star as Earth receives from the sun, the distance from would need to be roughly 8.8 * 10^6 times the current diameter of the observable universe.
I'll take your word for it on the lifespan; assuming you mean 10^9 when you say billion, that would be 10^20 years.

In turn, orbiting it from within its habitable zone are co-orbital binaries of one same star type: K5, 74% as wide, 69% as massive and only 16% as bright as our sun. Orbiting each of the binaries P-style, in turn, are co-orbits of Earth- to Venus-sized rocky planets.


With the specifics now in place, questions ensue:

1. How many Kardashev-type stars can fit within the 16-million-parsec parameters of the Z-Kardashev Galaxy?

Even just one star like this is enough to vaporize the entire universe. If you want a theoretical maximum, I don't really know how to estimate that. This galaxy is around 500 times the diameter of the Milky Way.

1. How far and how wide is the Kardashev-type star's habitable zone?

The habitable zone will be at around 1.7 * 10^7 Hubble lengths, or nearly a quintillion light-years, based on a naïve inverse square law calculation.

1. How many K5 binaries can co-orbit each other within the 100-billion-billion-year timespan?

What do you mean? How many systems could realistically form within this time? No K5V star is going to last 10^20 years.

1. How many of the K5 binary co-orbitals can fit inside the Kardashev-type star's habitable zone?

What is the mass of the Kardashev-type star? You gave its radius and temperature, but not mass. This information is necessary to determine the size of the hill sphere of the binaries.

1. How many Earth- or Venus-sized planets can fit within each K5 binary's gravitational pull within the 100-billion-billion-year timespan and not get themselves tidally locked?

About 60 AU is the minimum distance from the binary star for a planet's tidal locking time to be less that 10^20 years, based on Wikipedia's formula. However, since none of these stars will last that long anyway, the planet only needs to avoid tidal locking for the lifetime of the star (~25 Gyr), which gives us a much more manageable ~1.5 AU minimum distance to avoid tidal locking.

Out of curiosity, why are you calling it Kardashev? Does it have to do with the Kardashev scale, or is it something else?

 

[RaptorWolf]

I don't really understand how this is supposed to work, on any level. Why doesn't the heat radiate out like it normally would?

It's how white dwarves get so bright for so long.

What do you mean? How many systems could realistically form within this time? No K5V star is going to last 10^20 years.

How can you miss such a clear question? I mean, haven't you read PlanetPlanet?

What is the mass of the Kardashev-type star? You gave its radius and temperature, but not mass.

Mass does not correlate to luminosity.

Out of curiosity, why are you calling it Kardashev? Does it have to do with the Kardashev scale, or is it something else?

Partly. But "Kardashev" more importantly equates to "artificial", as in "created by some civilization more advanced that ours currently is". And calling the galaxy "Z-Kardashev" implies that the technology used to create this galaxy is rated "Type Z" on the scale.

 

[Workable Goblin]

It's how white dwarves get so bright for so long.

White dwarves are actually really dim, though. They're hot, but their small size means that they don't actually radiate much energy (which is why they're hot; they can't be cooled very efficiently). There's a reason that they're way below the main sequence on the Hertzsprung-Russell diagram.

Mass does not correlate to luminosity.

I mean....yes it does? In any case, mass is really important here because such a large hot object is almost certainly not going to be stable, but the exact direction it's going to be unstable is probably going to depend on the mass (whether it collapses into a black hole or explodes...I'm leaning towards "explodes" because the radiation pressure exerted internally by something in the terakelvin range is going to be incredibly large)

 

[RaptorWolf]

I mean....yes it does? In any case, mass is really important here because such a large hot object is almost certainly not going to be stable, but the exact direction it's going to be unstable is probably going to depend on the mass (whether it collapses into a black hole or explodes...I'm leaning towards "explodes" because the radiation pressure exerted internally by something in the terakelvin range is going to be incredibly large)

Tell that to OmniCalculator.

 

[Workable Goblin]

Tell that to OmniCalculator.

The calculator is grossly oversimplified. Yes, mathematically you can calculate the luminosity from just knowing the surface area and temperature of the star (and assuming it radiates as a black body, which is usually a fairly good approximation), but in reality those quantities depend on the mass, therefore mass is entering as an undeclared root variable in the calculator. For example, the core temperature of a larger star will be higher because a higher radiation pressure is necessary to keep it from collapsing (i.e., to maintain a steady-state), and this then means that energy production will be higher, meaning that the star as a whole will be hotter, meaning that it will be more luminous (not to mention larger, of course). This is why spectral class is closely related to stellar mass.

The calculator is assuming basically an ordinary star, and really isn't going to work right if you put in objects that are way outside of what would normally be physically possible (which an object--at this point we might as well dispense with calling it a star--heated to terakelvin temperatures definitely is; that's the kind of temperatures you would see shortly after the Big Bang!). You're basically picking a temperature and diameter arbitrarily and not really looking at whether they're physically realizable; again, the object you describe would probably either collapse into a black hole or explode, neither of which is particularly useful (well, a black hole might be useful for Sufficiently Advanced people)

 

[BrobDingnag]

Theoretically, it will expand the giant star's lifespan to 100 billion billion years (no, this is not a typo.)

If this is really what you’re going for–and since you’re seeking to engineer a solar system, it almost certainly is–why not simply have a galaxy’s worth of red dwarfs with their fusion maintained inside massive constructed external magnetospheric guides for the purpose of extending their respective lifespans? That gets you the extra “living time” a civilization seeking to reverse entropy would need to work on those equations without the mess of having to build your own star (and also orders of magnitude less complex infrastructure to keep stars burning).

 

[RaptorWolf]

If this is really what you’re going for–and since you’re seeking to engineer a solar system, it almost certainly is–why not simply have a galaxy’s worth of red dwarfs with their fusion maintained inside massive constructed external magnetospheric guides for the purpose of extending their respective lifespans? That gets you the extra “living time” a civilization seeking to reverse entropy would need to work on those equations without the mess of having to build your own star (and also orders of magnitude less complex infrastructure to keep stars burning).

Because red dwarves--yes, dwarves--are so tiny that the orbiting planets won't have days or nights, just eternal darkness on one side and eternal light on another. No Earth form can survive that.

 

[Vladyslav]

eternal light on another. No Earth form can survive that.

Me when you say that polar regions are uninhabited because of the polar day

If you have budget for this Supermegahyperstar (Am I right this should be artificial object?) you can use this resources for support of the planets' rotation or gene engineering to adapt to the eternal day

 

[BrobDingnag]

Because red dwarves--yes, dwarves--are so tiny that the orbiting planets won't have days or nights, just eternal darkness on one side and eternal light on another. No Earth form can survive that.

Is it a guarantee that all red dwarfs have their habitable zones inside the tidal lock region?

 

[Vladyslav]

Is it a guarantee that all red dwarfs have their habitable zones inside the tidal lock region?

A planet with a large orbital eccentricity may not be tidally locked, but on trillion-year scales all orbits tend to be circular unless the system breaks apart due to dynamical instability.

 

[Jürgen]

Is it a guarantee that all red dwarfs have their habitable zones inside the tidal lock region?

There’s a easy way around it, simply go with a hot gas giant with a habitable moon.

 

[BrobDingnag]

There’s an easy way around it, simply go with a hot gas giant with a habitable moon.

Klemperer rosette of Earth sized moons around a hot gas giant (mined for elements to transmute to serve the needs of the moons), itself part of a rosette of similar hot gas giants around a magnetospherically controlled red dwarf. To truly maximize the living space.

 

[RaptorWolf]

There’s a easy way around it, simply go with a hot gas giant with a habitable moon.

That presents the opposite extreme for Earth life--days and nights are too long, and years too short.

 

[BrobDingnag]

That presents the opposite extreme for Earth life--days and nights are too long, and years too short.

A year is a year. Tilt the moon axially with respect to the star. So you get a long night once a week (think: Ganymede); big deal. You can offset that by having the moon‘s orbit inclined with respect to the planet such that it never eclipses, too.

 

[HeedGreen]

Are Earth-like planets around white dwarf stars possible?

 

[Arkenfolm]

Are Earth-like planets around white dwarf stars possible?

Technically no, because they'd be tidally locked. In addition, they'd have to evolve life during the red giant phase and then migrate inward from further outside the habitable zone as the red giant dies.

 

[HeedGreen]

Technically no, because they'd be tidally locked. In addition, they'd have to evolve life during the red giant phase and then migrate inward from further outside the habitable zone as the red giant dies.

Tidally locked doesn't mean it wouldn't be habitable. If the atmosphere circulates temperature effectively, that is.

 

[Comte de Dordogne]

Tidally locked doesn't mean it wouldn't be habitable. If the atmosphere circulates temperature effectively, that is.

HeedGreen asked for an Earth-like planet, not just one with life.

Edit: I just realized that you were HeedGreen... Meh.

 

[BrobDingnag]

HeedGreen asked for an Earth-like planet, not just one with life.

That is him, and “Earth-like” can mean either “actually like Earth“ or simply having a high ESI, so that can be confusing.

 

[HeedGreen]

HeedGreen asked for an Earth-like planet, not just one with life.

Edit: I just realized that you were HeedGreen... Meh.

Earth like, as in, livable by humans.