Can Kerbol system exist in the real world

[dangerouspeople1]

So I checked the wiki and I saw Kerbol's mass is 1.7565670×10^28 kg and I also checked that the required mass to start fusion is about 1.5x10^29 kg. That says Kerbol shouldn't exist in the real world, but is there a way to create such a low mass star in the real world naturally? Like if some coincidental can start fusion even without enough mass?

[Steel]

The bigger issue is that the density of whatever Kerbin is made of is about an order of magnitude higher than any naturally known substance

[Gaarst]

Kerbol couldn't shine and Kerbin would have a density of 5 times that of lead (58 t/m³ against 11 t/m³).

The Kerbol is just not massive enough for nuclear fusion to trigger, with a mass of approximately 10 Jupiters. The mass of 13 Jupiters is usually the threshold between gas giants and brown dwarves, under this mass the body can barely fuse deuterium (the easiest element to fuse).

Actually the Kerbol would be surprisingly light compared to its radius (density of 230 kg/m³), 7 times less than that of the Sun.

Even Jool, the least dense of all planets (by far) would have to be made of titanium to have such a mass.

To sum up:

All planets are made of super dense material, Jool is made of Titanium, and the Sun could be used to seal a large bottle of wine.

[Findthepin1]

Maybe Kerbol isn't fusing. We have no proof that it is, and AFAIK nowhere in the game has it been stated that Kerbol is fusing.

[Gaarst]

Maybe Kerbol isn't fusing. We have no proof that it is, and AFAIK nowhere in the game has it been stated that Kerbol is fusing.

You know what a star is right ?

If it doesn't fuse, it's not a star. The end.

[sgt_flyer]

Eggrobin tried to put stock KSP's solar system in principia's n-body calculations roughly, having RSS planets in principia n-Body is as stable as the true solar system, while with KSP's stock planets / densities / orbital parameters the planet / moons orbits destabilise themselves quite fast (notably the joolian moons where some of them gets ejected from jool SOI ) so even if kerbol was undergoing fusion at his current parameters, the 'on rail' orbits with current parameters could only exist for a very short time before destabilising completely (and you'll end up having a complete orbital mess )

Edited October 18, 2015 by sgt_flyer

[lajoswinkler]

Kerbol is a burning ball of coal, obviously!

Nah, the system is tiny and has some properties of the real world. That does not work because the physical constants are all wrong.

[klesh]

If Kerbol were made to be the proper size for fission, how much bigger would it need to be? Would it's new radius be out past any planet's orbit?

[dangerouspeople1]

Eggrobin tried to put stock KSP's solar system in principia's n-body calculations roughly, having RSS planets in principia n-Body is as stable as the true solar system, while with KSP's stock planets / densities / orbital parameters the planet / moons orbits destabilise themselves quite fast (notably the joolian moons where some of them gets ejected from jool SOI ) so even if kerbol was undergoing fusion at his current parameters, the 'on rail' orbits with current parameters could only exist for a very short time before destabilising completely (and you'll end up having a complete orbital mess )

That might be fun

[Gaarst]

If Kerbol were made to be the proper size for fission, how much bigger would it need to be? Would it's new radius be out past any planet's orbit?

I think you mean fusion, not fission.

Anyway, it's not a question of size, but mass. According to the wiki, Kerbol is 1/3 of the Sun's radius but only 1/113 of its mass.

As I said in my previous post, astronomers usually consider that 13 times the mass of Jupiter is the lower limit to be able to fuse deuterium. Above this mass, the body is considered to be a brown dwarf.

To be able to sustain durable fusion reactions, it would have to weigh 0.07 solar masses (~75 Jovian masses, 8 Kerbol masses). It would then be classified as a red dwarf.

Red dwarves as small as 1/5 of the Sun's radius are known to exist, so on a size perspective, Kerbol wouldn't probably change much. On the other hand, it would have to multiply its mass by 10, and that would greatly affect orbits.

To sum up:

Kerbol wouldn't crash into Kerbin, Kerbin would crash into Kerbol.

[Majorjim!]

The kerbol system should be in universe sandbox. That would be ace!

[fredinno]

You know what a star is right ?

If it doesn't fuse, it's not a star. The end.

He was talking about if it was a particularly bright brown dwarf, but that seems unlikely. The planets could be made from a partularly high amount of iron and other dense metals, making them "iron planets" like Mercury, so the Kerbol System is probably in a relatively old part of a galaxy.

[klesh]

I think you mean fusion, not fission.

This is why I went to University to study music, not science. Lol.

Thanks for the explanation!

[maltesh]

Even Jool, the least dense of all planets (by far) would have to be made of titanium to have such a mass.

It doesn't, actually. Jool has about the mass and radius of Venus, and a density of about 4.7 g/cm^3. Earth is more dense than Jool is. (And, now that I look at it, Earth is more dense than Titanium as well.)

It's like Jool is a regular terrestrial planet in some kind of bizarre witness protection program.

Gilly also just scrapes by in the realm of known metallic elements, at 13.5 g/cc, that's about the density of Mercury or Plutonium. All the other planets and moons are more dense than Osmium at STP.

[Bill Phil]

No it could not exist. Everything is weird.

Now, if 1km in the game actually is 10 outside...?

[Gaarst]

It doesn't, actually. Jool has about the mass and radius of Venus, and a density of about 4.7 g/cm^3. Earth is more dense than Jool is. (And, now that I look at it, Earth is more dense than Titanium as well.)

It's like Jool is a regular terrestrial planet in some kind of bizarre witness protection program.

Gilly also just scrapes by in the realm of known metallic elements, at 13.5 g/cc, that's about the density of Mercury or Plutonium. All the other planets and moons are more dense than Osmium at STP.

Yes you're right.

When I looked at densities for having a comparison, I just took titanium because its density was close to Jool's, but I didn't pay attention to the significance of these numbers.

Anyway, my point was to show that even though Jool has realistic density for a planet, that would be for a terrestrial planet, not a gas giant.

I should have just said that Jool was 4 times as dense as Jupiter, that would have made more sense.

Thank you for correcting me !

[fredinno]

Yes you're right.

When I looked at densities for having a comparison, I just took titanium because its density was close to Jool's, but I didn't pay attention to the significance of these numbers.

Anyway, my point was to show that even though Jool has realistic density for a planet, that would be for a terrestrial planet, not a gas giant.

I should have just said that Jool was 4 times as dense as Jupiter, that would have made more sense.

Thank you for correcting me !

No, elements and metals are squished, and made more dense towards the core, so the planets can be made of less dense materials.

[ZetaX]

No, elements and metals are squished, and made more dense towards the core, so the planets can be made of less dense materials.

Ever tried actually squishing iron? Even the pressure in Earth's core cannot compress it much. Even less the pressure in Kerbin.

[lajoswinkler]

Ever tried actually squishing iron? Even the pressure in Earth's core cannot compress it much. Even less the pressure in Kerbin.

It can and it's not negligible. Even our oceans are considerably squished. Without that, they would be more than 10 m higher/deeper. Compressibility of liquids and solids is pretty realistic when incredible pressures are used, such as the ones inside planetary cores.

[ZetaX]

It can and it's not negligible. Even our oceans are considerably squished. Without that, they would be more than 10 m higher/deeper. Compressibility of liquids and solids is pretty realistic when incredible pressures are used, such as the ones inside planetary cores.

10m. Out of, say, 5km. This is totally neglegible. Especially as we are talking about a factor of more than 10 here, not just a percent more or less.

Also, I said "not much". Not "not at all".

[problemecium]

Short answer: Yes, but it isn't practical. At least it isn't as impractical as Minecraft would be xD

Substances do exist with higher densities than those calculable from the planets' sizes and gravities. An example is degenerate matter, the substance comprising white dwarfs. While composed of atomic nuclei and electrons, it doesn't form full atoms because the pressure is too high for electrons to leave their lowest energy states (as a result, white dwarfs exhibit an odd phenomenon where increasing their mass makes them smaller). This stuff isn't as dense as solid neutrons, but it is many times denser than "normal" matter.

That said, it's actually too dense, if I recall correctly. However, as we all know, mixtures of substances have a density between those of the densest and least dense constituents.

It is my general hypothesis that Kerbol is not a G-class star, but rather a white dwarf of class D-something-9 (look up white dwarf classes for details). Such stars tend to be very, very old and thus cooler than the stereotypical white dwarf, leading to a yellow (in the case of Kerbol) or red color (which has yet to be discovered due presumably to the limited age of the universe).

The Kerbolar system is probably in the far future, tens of billions of years from now, after some event occurred which caused the original "Kerbol" to partially break up. Most of its mass remained in the center, but due to the reduction in mass the star grew larger. The lost mass collected into small globules at varying distances from the star and, over millions or billions of years, accreted mass from interstellar dust to form the surfaces of the present-day planets and moons.

[dangerouspeople1]

So does that mean if I add more mass to it, it will become a type 1a supernova?also, can a whote dwarf be so light weight?

[problemecium]

Dunno.

If you add enough mass, sure. But for all I know you'd have to double it or more. I don't remember the mass of Kerbol. xP

EDIT: I looked it up. Kerbol is only 0.8% the mass of the Sun. More planet-size than star-size, really (almost the same mass as Jupiter). It'd have trouble even being a brown dwarf. But maybe it's a shard of a white dwarf - a tiny little fragment that got blown off alongside a bunch of even tinier fragments.

P.S.: According to this:

...with the exception of Vall's unfortunate placement next to Laythe and Tylo (from the latter of which it gets a big gravity assist after a few years), the Kerbolar system is stable for at least the first 100 years. Since any sane Kerballer is unlikely to simulate for more than 50 (c'mon guys), I say it counts if a Kerbolar system can be created IRL that lasts for at least a reasonable play length.

Edited October 19, 2015 by parameciumkid

[Deadpangod3]

but brown dwarfs can glow a bit too right? Unless Universe Sandbox has lied to me brown dwarfs can glow too, perhaps Kerbol is a very large brown dwarf?

[Gaarst]

but brown dwarfs can glow a bit too right? Unless Universe Sandbox has lied to me brown dwarfs can glow too, perhaps Kerbol is a very large brown dwarf?

They glow, but not much.

For a blackbody (stars can be considered as such) the wavelength of strongest light emission on the spectrum is given by Wien's Law. This wavelength depends only on temperature.

Also, the strength of this spectrum (power) is given by the Stefan-Boltzmann law and is proportional to the area of the star and its temperature to the power 4 !

The Sun, which has a surface temperature of 5800 K, has a peak wavelength of 500 nm.

As they don't fuse, brown dwarves are a lot cooler, rarely hotter than 2600K and often several times smaller than our Sun.

Assuming a really hot brown dwarf half the size of our Sun, this gives a peak wavelength of 1.1 µm and a total power that is 64 times weaker than that of our Sun. So not only the star would radiate much less than our Sun but it would also mostly radiate in the invisible infrared.

Actually, the Hertzprung-Russel diagram indicates that, on average, brown dwarves are 100 to over 10000 times less luminous than our Sun.