Or how about (full-sized) stars that are so cold that they are pitch black (which, of course, is a physical impossibility.)
As physically impossible as it may be, at least it makes for a great visit for explorers, though...
[Bug] Planet Surface Temps Hot as Stars - Breaks Immersion for Explorers
- Thread starter CMDR Galilean
- Start date
As physically impossible as it may be, at least it makes for a great visit for explorers, though...
Will do, and thanks for the suggestion!
Oh I have a whole list of quirks. Just tipping my toes in the water with this one.
Although admittedly, I haven't yet encountered any ELWs and WWs around neutron stars. Hmm, perhaps terraformed worlds around white dwarfs...
But yeah, it would certainly raise some eyebrows if you could land on such a planet and simply walk around.
You know, I had a nagging suspicion that something like that was the case, and that's why I suggested an alternative, far less invasive solution in the bug report.
There is a hint of deep red in that screenshot, so it ain't pitch black.
The coldest brown dwarfs are around room temperature, and therefore pretty darn close to black in visible light - but they nevertheless support deuterium fusion. Remember the temperature of the radiative surface doesn't have to be the same as the temperature in the region where fusion takes place. (That also applies to the temperature of atmospheres discussion up-thread - there is an important difference between heat and temperature and a very very thin atmosphere can have a very high temperature yet still carry almost no heat.)
Unsurprisingly we're finding more of these here infra-red-peak black bodies now JWST is there to find them via infra-red, and also confirming a few more suspects from WISE.
I realise these things like in your screenshot are more likely a Stellar Forge issue though - where is this one?
(Also, if you're looking up stuff about this part of stellar research on Wikipedia, be careful about the dates of articles, I just looked at a few at random out of the top 10 coldest stars and they're all well out of date)
I'm no physicist, but it is my understanding that after a certain size a star has to have fusion happening inside or it will collapse under its own gravity. I don't remember what the maximum size is, but I would guess that somewhere between Jupiter and maybe about twice as massive, give or take. And, of course, once the fusion reaction is kickstarted, its strength is pretty directly correlated to the mass of the star, so the more massive the star, the hotter (which is why cold stars tend to be very small, much smaller than our Sun, and very hot stars tend to be gigantic.)
In this case the "black" star in the screenshot is listed to have 116 solar masses, so I doubt it's physically possible for it to be that cold (its surface temperature is listed as 31 kelvin). There may be relatively cold stars out there, but I would guess they are very small, much smaller than the Sun.
The screenshot is from the Phimbeau AA-A h76 system.
There's another famous black star in the Splojeia AA-A h19 system (in this case with a surface temperature of 113 kelvin), if you want to make a tour.
Thanks for this bit of information - I had no idea such cold stars were even possible, regardless of their mass.
Ah! Almost, Stellar Forge. Almost.
Oh my, those are quite a distance away. But I'll be sure to visit them on my way to the Beagle Point.The screenshot is from the Phimbeau AA-A h76 system.
There's another famous black star in the Splojeia AA-A h19 system (in this case with a surface temperature of 113 kelvin), if you want to make a tour.
Several things going on here. The balance of fusion "pressure" versus gravity is what determines the fate of all main sequence stars, so yes that's true for "normal" stars. White, brown and black dwarfs aren't normal stars though...
You might be thinking of Chandraskhar's Limit where he showed that fusion plus electron degeneracy pressure in a white dwarf would still not be enough beyond 1.4 solar masses. So yes a black dwarf with 116 solar masses is unphysical and it must be a Stellar Forge issue. But even in a white dwarf it's not fusion that's preventing it from collapsing.
Brown dwarves aren't on the main sequence and the mass involved is WAY smaller. The limit between "actual brown dwarf with fusion" and "sub-stellar object" (as FFE calls them) or "hot Jupiter" as astro press releases call them, which have no fusion, is about 13 Jupiter masses. Not solar masses! 13 J-mass is enough to start deuterium fusion, which requires deuterium as a fuel and will stop when that runs out. At 65 masses you can "burn" lithium. At 80 J-masses you get "normal" hydrogen fusion and that's the line between brown dwarf and white dwarf.
The size of brown dwarfs and white dwarfs doesn't depend on "how much fusion" anyway though - there isn't enough fusion pressure to keep them at that size in the first place. They both depend on "electron degeneracy" which is what prevents them from shrinking down to a density where they would become a neutron star.
The limit of electron degeneracy pressure is about 1.4 solar masses so brown dwarfs are way, way off that limit and in no danger of further collapse.
All of which means these here "black" stars in ED are unphysical yes - not because they can't form in theory but because the theory would take trillions of years to play out, and we haven't had trillions of years yet...
13 J-mass (or 65...) as above. After 80 it's a white dwarf.
Yep this is a Stellar Forge issue for sure then. There is a pathway for a white dwarf to cool into a black dwarf in theory, but the theory requires the star to cool for longer than the present age of the universe. Order of 10 trillion years, so three orders of magnitude older than the universe. And as above, a white dwarf over 1.4 solar masses - so again, this black star is two orders of magnitude too massive - should have collapsed into a neutron star long before it got down to this temperature.
Thanks!The screenshot is from the Phimbeau AA-A h76 system.
There's another famous black star in the Splojeia AA-A h19 system (in this case with a surface temperature of 113 kelvin), if you want to make a tour.
Splojeia AA-A h19 - through the core and out the other side... blimey. That would be a "tour" alright!
Here's more stars for the tour, just looked this up:
- The coldest T-star is UGPS 0722-05
- The warmest Y-star is WISE 1738+2732
- The flat-out coldest known star (which is a Y, obviously) is WISE 0855−0714
All in the Bubble.
I should have specified that the "black star" in Phimbeau AA-A h76 not only has 116 solar masses but also a radius 8.4 times that of the Sun. Which, as far as I know, makes it physically impossible for it to have a surface temperature of 31 kelvin.
Degenerate matter stars don't need fusion to not collapse further, but they are, rather obviously, extremely dense (beyond all comprehension) extremely hot. While a white dwarf typically has a mass comparable that of the Sun, is radius is minuscule compared to it.
A black dwarf is a hypothetical object that's a white dwarf that has lost all of its thermal energy and become cold (and thus doesn't emit any light at all). However, quite obviously these are equally small. Also the current consensus is that these objects don't exist in this universe because there has not been even nearly enough time for any white dwarf to cool down enough.
Anyway, the game lists the star at Phimbeau AA-A h76 to be a Wolf-Rayet star, not a dwarf star. Wolf-Rayet stars are typically extremely hot. I have no idea what glitch caused these few to be this cold. Maybe some kind of bug?
Degenerate matter stars don't have to be extremely hot. The whole point here is that a body made of degenerate matter can be any temperature at all and will still not collapse, because degeneracy pressure prevents this collapse, in lieu of any thermal pressure.
White dwarfs are hot because they are still cooling off from their means of formation.
The surface of a late-M brown dwarf is not hot enough to melt tungsten. Sure it's hot but it's not "won't see that on Earth!" hot. (Not relevant to the situation with black stars, I appreciate, but I'm just emphasising that all combinations are possible really, high temperature low density or high temperature high density or low-low or high-high. It just depends how that particular lump of matter got there and at what point in time you observe it. High-high is notably not stable though and anything high-temperature becomes... lower temperature eventually. But we just discussed that we haven't had all the "eventually" yet.
Yeah. I just said that.
Wolf-Rayet stars in the real universe come in two families, both of which have a specific (unusual) composition of the original star and a specific lifecycle that gets them into the W-R state. I suppose it's possible Stellar Forge has accidentally invented a third family of stars with a weird and specific metallicity/composition and has decided those are W-R due to a classification error. That would have to work in conjunction with another bug which somehow allows super-fast cooling of stars.
Excellent read guys, thanks for that!
I have to bookmark this and take a peek next time I have time to play.
Meaning those stars are part of the real world catalogues integrated into the stellar forge? Do tue properties in-game match the real ones?
I have to bookmark this and take a peek next time I have time to play.
Hm - WISE 1738+2732 is not in the game - the other two are. There seem to be other stars from the same discovery paper (published 2011) that ARE present so I'm not sure how FDev have decided what cut of the data to take.