Build Your Own STARS! | Worldbuilding

Episode 6: Worldbuilding Stars and Solar Systems
In this video we discuss the creation of stars, determining which stars are best suited for worldbuilding life-bearing planets, as well as why stars are more likely to predict life than the planets life lives on.
---
WORLDBUILDING CORNER: www.worldbuildingcorner.com
Solar System Builder: www.worldbuildingcorner.com/resources
---
All music, images, and other media used in this video are available for commercial use with Creative Commons licensing, found on www.pixabay.com and www.pexels.com.

[@smergthedargon8974]

I'm pretty sure "red giant" is the name for mid-mass stars in their final stages of life, where they massively inflate in size, not an alternate name for red dwarfs.

[@WorldbuildingCorner]

Correct, thank you for picking this up! Importantly for worldbuilding, a red giant is quite unlikely to host life, as any previously habitable planets are likely to be either consumed by the star, or at least no longer fall within the habitable zone. In contrast, red dwarfs can in theory host life, though it would look quite different to life on earth.

[@carlborneke8641]

@@WorldbuildingCorner How likely is it for planets around red dwarfs to be tidally locked and would they still be able to support life in their twilight zone?

[@user-mt1qi4vd1z]

@@carlborneke8641 very high probability they are locked. Support of life depends on luminosity and planet gravity

[@potatoheadpokemario1931]

@@WorldbuildingCorner why couldn't life exist on a red giant on a planet in the new habitable zone?

[@falseprophet1024]

​@PoTato Head PokéMario That new goldilocks zone doesn't last long enough for life to evolve.

[@draugarnatt3816]

A very good video over all, much appreciated! As an astrophysicist and fellow worldbuilder of a circumbinary planet, I'd like to make some minor corrections though, hopefully without sounding like a smartass: - First, a rogue planet getting captured by a star (binary stars even) would likely have a very eccentric orbit initially, though it can stabilize over a sufficiently long time. - 2:50 there are more accurate equations for stellar lifetimes but it's sufficient for worldbuilding (and in fact, for much of astronomy too), keep in mind though that there is variance even for given stellar parameters. Also, the Sun is expected to remain on the main sequence for another 5 billion years. In any case, I think you could include higher mass stars up to late A-type stars since it's possible that life on other planets can evolve faster than it did on Earth (even on our planet, life evolved at different paces in different epochs and ecological niches), though I agree that I wouldn't go beyond 2 Solar masses unless the lifeforms are *VERY* alien. But hey, suspension of disbelief is a thing, so unless you write very hard sci-fi you can make it work. - 3:50 Stars don't go supernova below at least 8 Solar masses. - 6:40 I wouldn't exclude red dwarf stars from hosting habitable planets. Life would be quite different on such a planet, but chances are it would easily adapt to such things as tidal locking. The flare eruptions might be the biggest issue here, but not all M-dwarfs are flare stars, and a planet with a sufficiently strong magnetic field could cope with that (might lead to very intense aurorae on the planet). Your work on the binary system is quite impressive actually, some nitpicking: - 10:30 some parameters are odd. For once, why did you calculate radius and diameter separately? The mass-radius-relation is also different for different types of stars, the one you used works well for more massive stars, for smaller stars it'd be closer to R ~ M^0.8 and for fully convective stars, like your red dwarf, it'd be almost linear. In other words, it's not a simple power law. Lastly, there seems to be a math error regarding the density; smaller MS stars should have a *higher* density than larger ones. Density is mass per volume, use that to calculate it instead of the relation shown here. - 12:20 we know stable binary systems with smaller separation distances but I agree that this can lead to complications depending on the star. If you have two red dwarfs, you can easily bring them together much closer together though. - 14:00 not really. You see, even 0.1 AU would still be about 10x the diameter of the Sun or Flavus, which is way more than enough to clearly separate the two stars in the sky most of the time. Also, while Rufus is much dimmer than Flavus, the difference is not large enough to outshine it. You would still end up with a Tatooine-esque view of the binary suns, but one of them is just significantly brighter (i.e. if Flavus is as bright as the Sun, Rufus would still about as bright as the Sun is from Saturn). Again, I enjoyed your video very much, and love how informative it is. These are just a couple of suggestions and corrections that you (and others) might find helpful. Keep up the good work!

[@WorldbuildingCorner]

Wow, thank you for your detailed comment! As a non-astrophysicist, I greatly appreciate the professional feedback! I will respond to each of your points as best I can. - I suspected a rogue planet would take some time to stabilise, but wasn't able to determine how long 'a sufficiently long time' would be haha. Arbitrarily I went with 1 billion years. Is there a means of calculating this time? - Your comment re: stellar lifetimes is interesting! I am not sure I would want to 'speed up' evolution unless magic was involved, but good to know it can a bit at least haha. - I did know this, but good to explicitly point it out. - I love the idea of super intense aurorae on the hypothetical planet orbiting the M-dwarf! Good to know they could host life, though I do prefer my worlds and life-forms to be more 'earth-like', so would probably steer away from it. - In my spreadsheet (which is available on worldbuildingcorner.com under resources), I used R~M^0.8 for Rufus, I had researched that larger stars used ^0.5, smaller used ^0.8. Is there a point where it steers towards linearity? Also good catch re: the density, it was a math error in the spreadsheet that I copied across into the video. - Good to know! A super tight binary red dwarf system would be very cool. - I am actually super pleased to hear that both stars would likely be visible! I tried to research this as much as I could but the best I could find was that the perspective luminosity of Rufus was way too dim compared to Flavus. I wanted the two stars visible, and conceded that they wouldn't be based on the information I had. This is great to know! Thank you again for your comment and information, always happy to have feedback from those more in-the-know than I!

[@draugarnatt3816]

@@WorldbuildingCorner glad you found it helpful, I'll address some of the points here: - You could with simulations (I can't think of a specific program rn), but it's probably an overkill. These processes are likely very chaotic, but there is a chance that conditions are right for it to work out as intended. So I'd leave it as it is. - Understandable, we don't know everything that has driven/drives evolution here on Earth, so it's a good idea to stick to patterns we know for worldbuilding. For speculative evolution it would be very cool to explore though. - Life around an M-dwarf would certainly be interesting and alien. It might not have a day-night-cycle (or a very slow one) and thus animals would have a completely different circadian rhythm, perhaps more akin to hibernation, or polyphasic like cats. - Ah, thanks for pointing that out, just saw it. It approaches linearity for red dwarfs, below 0.6 Solar masses. The higher the mass, the smaller the exponent. It almost looks logarithmic. If you want to read more: personal.psu.edu/rbc3/A534/lec18.pdf For worldbuilding purposes your approximation works very well, and there is of course variation even in real stars because, as someone studying stars I can confirm that stars are really damn weird lol - You can definitely have cool Tatooine-esque sunsets (or suns-sets? haha) on your world with those stars! Your videos and website are very helpful btw, especially when it comes to building different cultures. I'm working on a Sword & Sorcery world orbiting a pair of binary stars in a very realistic configuration, and the implications it would have for the cultures on such a world are very interesting!

[@WorldbuildingCorner]

@@draugarnatt3816 Thank you for your detailed response :) I will be sure to give the resource you have linked a read! I am glad you are finding the content useful! Your S&S world sounds interesting, the cultural implications of even small changes from real-life are fascinating. Good luck with your project!

[@andresmarrero8666]

Wouldn't stars be natural synthesis reactors? In this case they don't expire due to running out of materials but because they are overloaded with too much energy causing them to bloat until they loose cohesion and pop. That would mean that stars in this universe would have a higher luminosity and planets near bigger stars would have more abundant life. The more massive stars would also live longer as they have more material to fuse and maintain the synthetic systems taking place. That would enhance the popping though akin to covering a water hose with a balloon. The matter is regulating and filtering the synthetic processes, but since gravity is also a factor whether a large star becomes a black hole or a white hole would depend on how the equilibrium of synthetic and fusion systems broke down.

[@clairetellkamp6253]

No, the stars are severance reactors. He explained that processes that increase entropy do not actually increase entropy, but send their energy to the other universe. (I'm not actually sure how this works, though, because entropy is not a form of energy, but a description of the state of energy.)

[@andresmarrero8666]

@@clairetellkamp6253 it is the black holes that are severance reactors. He never said anything about how stars interact with the synthetic/severance, but sense stars generate power they would be synthetic reactors not severance reactors as the energy output isn't seemingly decreasing, the energy isn't being sent.

[@clairetellkamp6253]

@@andresmarrero8666 He actually did. He said when fire burns, they increase entropy in the real world. In his fictional world, they wouldn't increase entropy, but instead send that energy into the other world. On the scale of a fire, though, it wouldn't be much. But he explained that the scale of a star would have much more of an effect, and that energy gets sent to the other universe. He did not say that black holes are severance reactors afaik. It might make sense that they are, because they can trap light. But additionally, the stars' energy outputs not decreasing is a problem with this magic system that I brought up in an earlier video. The way he explained it, stars should not exist. They should be sending all of their energy to the other universe. The way you are describing it, stars wouldn't be stars, they would just be white holes.

[@keithos3076]

Hi. I'm really enjoying your content. I'm not sure how to use your spreadsheet. I copied it to my drive but I'm not sure what I can change myself and what needs to be left alone. You don't show yourself using the spreadsheet in the video so I'm not sure how to use it. It would help if you made a video or something to explain how the spreadsheet works. Thanks keep making videos.

[@beddo6662]

Loving this content so far. Really easy to digest yet entertaining to watch. Looking forward too the next one.

[@WorldbuildingCorner]

Thanks for the positive feedback! Welcome to the channel :)

[@Frostfly]

I think you missed a point here. When Rufus is eclipsing Flavus. It's gonna be big enough to cause a change not just of the color, but of the light levels. It will get quite a bit darker.

[@alexanderzippel8809]

imagine the stories of tribal people trying to explain why the sun is changing colors time and time again. UHHH the potential

[@deltainfinium869]

You mentioned that the stages between main sequence and death are often too violent for life, and while I agree, may I offer a counterpoint: Stars that are just barely large enough to fuse helium and are currently doing so are theoretically, although variable, long-lived enough that planets in its habitable zone could develop life. I imagine that a super-earth with a strong magnetic field could probably support life around one such objct.

[@eddiems]

HI! I compared the values in the video with your spreadsheet and i didn't understand the cells J5 and J6, maybe because english is not my first language. I thought this cells show the colours of the stars, but you said the FLAVUS was yellow and RUFUS was red, but in the spreadsheet shows light green and purple. Can you explain more about that? I was really amazed with the possibility of stars with different colours in the sky

[@WorldbuildingCorner]

Yes absolutely, in the spreadsheet J5 and J6 refer to the preferred colour of plants (flora) based on the light wavelength produced by the star(s). We expect plants to prefer to either maximally absorb as much light as possible from the star (preferred colour A), or reflect as much light as possible to prevent burning/mutation (preferred colour B). However, note that these are just preferred colours (on earth, our plants preferred colour is green, maximally absorbing light from our star), but there are certainly plants with other colours, absorbing other wavelengths of light that succeed just fine. Hope this helps!

[@ArcaneNiles17]

I think the density may be calculated incorrectly on the spreadsheet since density is m/V and you have it as r^(1/8)

[@voidwyrm6149]

the technical definition of a brown dwarf is a substellar object that is not massive enough to fuse hydrogen-1 into hydrogen-2 but is massive enough to fuse hydrogen-2 into helium-3

[@Schattennebel]

I wanted to create a "believable" system for my storys so I tried this after some reading. The main star of the system is a K3V star "Orange Dwarf Star" with 0,78 mass of the sun and with 0,28 luminosity of the sun. It should burn for about 28 billion years wich means enough time for live to enjoy its warmth. In 300 AU from that star a M3V star or "Red Dwarf Star" orbits it with 0,30 masses of the sun and about 0,01 luminosity of the sun with a lifespan of 300 billion years. Should be far enough. I also planned to put the world of my storys in a 0,78 AU orbit around the K-type star for a tiny bit cooler climate than our Earth.

[@WorldbuildingCorner]

Sounds like an interesting system! I popped your K class star into the solar system spreadsheet (link in description) and it looks like with a star of 0.78 solar masses, it's luminosity would be 0.419 that of our sun, which in turn gives a lifetime of 18.616 billion years and a habitable zone from 0.615AU to 0.886AU. The M class star is so far away at 300AU that it wouldn't affect the habitable zone of your system too much. Looks like your planet's orbit at 0.78AU from the parent star is perfect! I always like the idea of planets with an orbit less than 1AU because I like worldbuilding with shorter years. It feels... neater haha.

[@hungvu262]

Was able to configure the spreadsheet to fit two stars, stumpted on inner habitable zoen of solar system though.

[@WorldbuildingCorner]

The spreadsheet should work (and is designed for) two stars! Also, the inner habitable zone of the solar system for two stars √((L1+L2)/1.1), where L1 is the luminosity of the first star, and L2 is the luminosity of the second. Hope this is helpful!

[@hungvu262]

@@WorldbuildingCorner Oh, thought you were talking about artexians sheet.

[@spookyshoe7411]

Great video and your content is great but I'm just wondering how you would calculate the perspective size of the stars from the planet. I tried to find it on my own, and i was stumped, and when I used the equation that was used for the perspective size of the moons it didn't seem right, so if you could help that would be very appreciated!

[@clairetellkamp6253]

A star the size of our sun will not go supernova, it will expand into a red giant before dwindling down to a white dwarf, since they aren't large enough to overcome electron degeneracy pressure, and finally fizzling out into a black dwarf. Larger stars go supernova and can end up as neutron stars, or, if they overcome neutron degeneracy pressure, become black holes. For anyone interested, electron degeneracy pressure is essentially the resistance of electrons to occupy the same space as other electrons of identical spins at the same energy level. All electrons start out at the lowest energy state, and the gravitation pressure inwards on a star drives electrons up in energy states. Each energy level can only be occupied by two electrons at a time, (there are two directions of spin, and each energy level can only hold one electron of each directional spin). You have to have increasing amounts of energy (from the gravitational pressure), in order to get electrons to make the jump from the lowest energy to state to the next available "rung" on the energy ladder. If at any point, the pressure outwards as a result of the electrons resisting this energy jump matches the gravitational pressure inwards, the star stops shrinking and holds steady. This is what our sun will become: a white dwarf. After a supernova, a larger star can over come this electron degeneracy pressure and keep shrinking, and thus becoming more dense. But it will eventually hit a point where the neutrons start resisting the energy level jump. Yada yada yada, neutron degeneracy pressure (reread the electron degeneracy pressure explanation and replace "electron" with "neutron.") If a star overcomes neutron degeneracy pressure, it can shrink down into a black hole. Theoretically, it should shrink infinitely, but there are theories that it does stop at some point.

[@tubepkn]

I looked at the spreadsheet and see that Radius and Circumference of both the primary and secondary star are identical. That seems incorrect to me, or am I missing something?

[@440hurtz4]

4:18 There are also clasifications for brown dwarf put after M types called L Y and T, and Wolf-Rayet stars, WR types above O. 6:50 M type stars can host life, but that life would need to be on a planet very close to that star. Also, red giants and red dwarfs are diffrent. Red giants (Class M III) are dyeing stars that are around the mass of the sun, and as they expand, they cool because there is more surface area. Red dwarfs (Class M V) are the ones you described. The MK-System accounts for the branches of evolution in a star and because of this, calling a star an M, K, or G type is just not enough information. After the steller class, you just put a roman numeral to tell what star it is really. 0 (Hypergiants), Ia and Ib (Supergiants), II (Bright giants, sometimes lumped in with Supergiants), III (Giants), IV (Subgiants), V (Main sequence THE MOST COMMON STAR TYPE and the only one able to support complex life), VI (Subdwarfs), and VII (White dwarfs, I honestly don't know why this exists as there is a separate letter for white dwarfs, D types). I dont know why there are white dwarf classes, but not for neutron stars but whatever.

[@potatoheadpokemario1931]

I thought a red dwarf was a main sequence star and red giants are what happens after the main sequence

[@Liethen]

I would think due to the difference in luminosity that when Rufus eclipses Flavus it would significantly reduce the amount of heat reaching the planet. If anything, I would expect a notable month long cycle of temperature as the amount of heat reaching the planet would drop by half-ish every few weeks as Rufus blocks more of Flavus.

[@broEye1]

From what I've heard and read, a red dwarf is a very bad place to be orbiting. They're far more volatile, having eruptions and flares of a much larger scale that could easily wreck a planet and blast away its atmosphere. On a different note, one other point that could be present and have some significance to the world's traditions or mythologies is the *nova*. With a binary system orbiting so close together, there will always be a chance for them to get close enough that the red dwarf's gravity sucks in some of the other star's hydrogen, resulting in a sudden massive increase to its luminosity. Every now and then, over the eons, the sun would seem to suddenly become blindingly brighter for a brief period.

[@recursiveslacker7730]

Red dwarf planets are also likely to be tidally locked.

[@scottmm78]

Missed a great opportunity to have hossest in blue and coolest in red like how start are

[@AI_ALVAREZ_INTELLIGENCE_AI]

If we reach space age we able build Stellaris star building

[@GentlemensClubHolyEdition]

No purple starts? ;-;

[@sproge2142]

Whomever named the red giant/dwarf "M class" is clearly not a Star Trek fan and should therefor be fired.

[@MessedUpSystem]

"If you're using a system with more than 2 stars..." No just don't it's unstable as hell and very likely wouldn't support any sort of life hahaha

[@spookyshoe7411]

your google sheets make no sense and its the worst thing ive ever used