Would an endothermic star be possible?

Real world stars are a mass of exothermic nuclear reactions. But what if there were some sort of star-like astrological phenomenon that somehow underwent an endothermic reaction?

I would like to know if the existance of this 'endothermic star' could be justified. Scientific explanations are preferred, but I'm willing to stretch to magic means if there are no plausible scientific explanations.

Further Clarification: Preferably something that has gravity/can be orbited, but ultimately anything that would have a cooling effect on other nearby celestial bodies.

Note: I'm not actively writing a story, this is purely hypothetical for the time being.

• When you say star-like what do you mean? You take away the exothermic nuclear reactions and you don't really have anything that resembles a star. – Joe Kissling Mar 29 '17 at 4:27
• magic and physics together? – L.Dutch - Reinstate Monica Mar 29 '17 at 4:35
• @JoeKissling Preferably something that has gravity/can be orbited, but ultimately anything that would have a cooling effect on other nearby astral bodies. – Pharap Mar 29 '17 at 4:35
• Afaik physics goes with what we know about our world, magic goes against what we know... – L.Dutch - Reinstate Monica Mar 29 '17 at 4:38
• If even The Doctor doesn't want a piece of this, you have to ask yourself .. how far from the pack have you strayed? :) – Lightness Races with Monica Mar 29 '17 at 10:10

Technically those do exist, they are called Type II Supernova, though the endothermic part is very brief and then followed by a very exothermic reaction. The exothermic nuclear reaction is what make a star a star. Once the nuclear reaction starts taking more energy than it gives off, like when attempting to fuse iron in large stars, it collapses in on itself. Stars are held up by radiation pressure from the nuclear fusion, without it they cease to be stars.

Otherwise, A star is by its very nature an exothermic reaction.

Edit

Has mass but does not warm a object around it. You could orbit a black hole that does not have an accretion disk. The cooling would come from space itself and for all practical purposes the black hole would give off very little heat.

• On this note, if a black hole of equal mass was swapped for our star, the gravitational effects on our planet would remain unchanged. It would take eight and a half minutes for us to notice this. It has been theorized that there are solar systems made up of trapped rouge planets with black holes at their centers, however due to Hawking radiation, we can't see them since they take in more energy than they release. We have to see it to know it exists. That larger a black hold the longer it takes for it to disperse. One the size of our star would take twice the time our universe has existed. – Kayot Mar 29 '17 at 12:53
• @Kayot Check your math. It would take way longer for a black hole the mass of our sun to evaporate than a mere 28,000,000,000 years. It'd be closer to 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 or 10^67 years. – Shufflepants Mar 29 '17 at 14:07
• @Charles Yes, of course in a vacuum. Also, unless otherwise specified, all animals are assumed to be perfectly spherical, identical, and frictionless. But even accounting for a lack hole taking on more mass in the near term, the figure is still approximately correct considering adding on 10^25 * 10^10 years = 10^35 years only affects the time by 10^(-30)% – Shufflepants Mar 29 '17 at 17:13
• Only if protons decay. The lower bound for their life is 10^43 years if I recall correctly. It's even worse than that, not only is there the interstellar medium but even absorbing the cosmic microwave background photons can outpace the loss to hawking radiation. – Joe Kissling Mar 29 '17 at 17:14
• @JoeKissling 10^29 years is still approximately 0% of 10^67 years. – Shufflepants Mar 29 '17 at 17:46

There's a problem here: nothing is colder than deep space.

Since there is no interstellar medium, the only way heat transfers in space is by radiation. Any object facing deep space and not illuminated by a star or itself will, left on its own, gradually cool to a little over absolute zero, heated only by the cosmic microwave background radiation.

There's no way to "suck" heat out of something that's not being radiated in that direction. You could have planets orbiting a dead star that emits nothing, or possibly a planet that is a wanderer, and they would be extremely cold; any remaining atmosphere lying frozen as a blanket of snow.

• This. You could spin it just another way: it is not possible to create an endothermic star (by your argument) because "endothermic" means "takes thermal energy from the environment" and "deep space" means "there is no environment to take thermal energy from" (if you ignore any unhappy photons whizzing around and being caught, which is hardly what one would figure as "endothermic"). – AnoE Mar 29 '17 at 13:09
• Black holes are colder than background. If a planet orbits a black hole even the faint cosmic background radiation from that direction is sucked up. However this wouldn't produce much of a cooling effect under most circumstances, unless the black hole is very large and close. (super massive to minimize tidal heating) – Donald Hobson Mar 29 '17 at 13:11
• Yes, @DonaldHobson, technically being "behind" a black hole will shield you from some part of the background radiation. But... if you use "endothermic" like "exothermic", i.e., in significant sizes, I'm pretty sure the OP did not think of this minuscule amount of energy (the background is what, 2°K?). – AnoE Mar 29 '17 at 13:24
• Are you sure that space is cold? <Warning: Tv Tropes link> – xDaizu Mar 29 '17 at 14:30
• @DonaldHobson: Black holes may be colder than space and thus absorb energy from it, but when you're close to a black hole, general relativity says that the CMB that reaches you from the non-black hole-covered area of space is blue-shifted, so the effects may cancel each other out; someone should do the math. – mic_e Mar 29 '17 at 15:54

This is probably nutty, but something like adiabatic magnetic refrigeration might work. https://en.wikipedia.org/wiki/Magnetic_refrigeration

Imagine taking the iron core of a dead star. Apply a mind-bogglingly large external magnetic field, using something like solar-system-wide Helmholtz coils. Maybe Magneto could do it. Anyway, once the system equilibrates to the new high field, the iron core will be magnetized, meaning all of its magnetic domains are aligned along the field.

Now start to lower the externally applied magnetic field. I'm not sure how to estimate over what timescale it can be lowered, but there would be an incredible amount of energy stored in a stellar core sized chunk of iron, so I would guess centuries just comparing that mass to a standard adiabetic magnetization refrigerator mass.

As the magnetic field decreases, the core's magnetic domains will start to randomize by absorption of thermal energy. But until the magnetic field is zero, the domains will reorient themselves to this lower energy state, resulting in a "spontaneous" decrease in entropy, cooling the body. So over whatever time scale you lower the magnetic field, the body would overall be colder than surrounding space, with the cooling power equal to the decrease in stored magnetic energy over time.

It would be artificial to set up, but in principle it could be a relic from an older hyper-advanced civilization, with the magnetic field machinery just now decaying when we find it.

• Not much spare thermal energy floating out there in space, but I like the concept. – nijineko Mar 29 '17 at 20:03
• Initially the thermal energy comes from the core's internal state. If you have perfectly aligned magnetic domains, then any temperature other than absolute zero has enough thermal energy to randomize some of them. – thegreatemu Mar 29 '17 at 21:26
• I like it, but won't gravity still make it burn? – ShadSterling Mar 30 '17 at 1:38
• @Polyergic If it really were a core of iron, it wouldn't burn. As far as we know, everything heaver than iron in the universe was made in supernovae, not stellar fusion. Of course it might just collapse if you tried to make it too big. – thegreatemu Mar 30 '17 at 15:21
• @nijineko When you're talking about deep space, the random atoms of helium and hydrogen and whatever that exist between stars are functionally the same as thermal energy. Though they would not drive this refrigerator. Light would though. – Xalorous Mar 31 '17 at 3:28

Black holes are endothermic in a sense, although their swathe of destruction causes an exothermic signature.

I guess cold neutron stars could be endothermic, as their neutrons evaporate. It's complex, because these mechanisms are quantum physical rather than chemical, but in the sense of absorbing heat rather than emitting light you have to go to the dark side - certainly endothermic stars couldn't emit black body radiation.

• For practical purposes a solar mass black hole is cold. A neutron star is a good idea if you want to magic a way to cool it. Otherwise, you won't get a cold one for a very very long time. – Joe Kissling Mar 29 '17 at 4:45
• Not actually true. Black holes emit Hawking radiation, and actually lose mass over time when matter is not falling in. In the long run, they will lose more energy than they gain. That said, the long run is very long indeed and they can act as endothermic bodies for a very long time if there is sufficient material to feed them. – James Hollis Mar 29 '17 at 18:02

For the purposes of writing a science fiction story, these answers are not necessarily satisfactory. The concept of an endothermic star might appear in the mind to be an icy blue sphere of radiating energies unknown to modern physics. In reality, the concept is quite different.

For something to be endothermic, it must absorb energy from its surroundings, but this is not seen in space typically. In space, where the radiant temperature is a few Kelvin, there are limited sources of energy for such a star to feed off of. That is, they are limited but not nonexistent.

Recently, the discovery of gravitational waves has made ripples (sorry) in the scientific community. It is conceivable, with a bit of a stretch, that an endothermic star could be at a nexus point between multiple binary star systems, where each creates gravitational waves that pass over the endothermic star, and the waves enter a superposition of energy at this point.

The energy in the space of the star could be used to help heavier elements undergo nuclear fusion (remember that the fusion of elements heavier than iron requires more energy than it could release, making the process endothermic). This star would still release some light, and thus it would work perfectly in a science fiction novel. Attached is an image of what the system would look like, with the scale of distance being in hundreds of light years.

• Welcome to WorldBuilding! Interesting answer. If you have the time please take the tour and visit the help center to learn more about the site. Have fun! – Sec SE - clear Monica's name Mar 29 '17 at 18:01
• To be macroscopic those would have to be some incredibly energetic gravity waves. Like, take a few hundred extremely massive black holes (each maybe the mass of the Laniakea Supercluster), arranged in small groups with stable orbits at nontrivial fractions of $c$, and the groups in a dyson-swarm-like arrangement around the nexus. (And I thought the empire's Maw was hard to navigate!) Somehow, that level of ridiculous makes me like the idea more. (Experiment to prevent heat-death fails because nexus cancels out... something...) – ShadSterling Mar 30 '17 at 1:36

Would a black dwarf be endothermic? Black dwarf stars are a theoretical type of star that has not yet had sufficient time to form in the universe. It is hypothesised that our own Sun may end its days as a black dwarf a quadrillion years from now.

• Black dwarves would not be endothermic. – kingledion Mar 30 '17 at 1:10
• Welcome to WorldBuilding! If you have the time please take the tour and visit the help center to learn more about the site. According to the link you provided a black dwarf would not be endothermic, just not very hot. But I think this is a good answer as black dwarfs haven't been mentioned as of yet and are a nice addition. Could you think of a sci-fi way of making a black dwarf appear to be endothermic? +1 from me anyways – Sec SE - clear Monica's name Mar 30 '17 at 7:08
• @Secespitus How is it a good answer if it is wrong? I don't mean to discourage the OP either but answers are good only if they are true. If this was just a doubt, it would be better suited as a comment. Or even better, the OP could have done more research and found it out. – ghosts_in_the_code Mar 30 '17 at 7:57
• @ghosts_in_the_code The question includes "magic" as a tag. Therefore I don't think it's necessary to be "correct" in this question. That's why I asked the answerer for an idea about how to make this work by using a black dwarf as a starting point and adding sci-fi ideas. – Sec SE - clear Monica's name Mar 30 '17 at 8:21
• @Secespitus Ok then – ghosts_in_the_code Mar 30 '17 at 8:25

There is a very general problem with your request: A true and permanent radiation sink violates the second law of thermodynamics (you take entropy away from the universe). This law is among the most universal laws in physics; it governs black bodies and black holes, indeed it probably governs the universe as an entity as well.1

Now that law only applies to closed systems. Maybe what you are looking for is a processor cooler at a stellar scale? That is, a mechanism to guide the heat away from the star and emit it "somewhere else". If you don't want to have an orbiting heat pipe2 (it's orbiting so that it's always behind the cold star and does not spoil the view) I'd suggest a mechanism like magical micro mirrors (the marketing term was m3) that reflect incoming radiation at an angle perpendicular to all three spatial dimensions. Poof, gone. Make sure it is a one-way mirror though (you know, the second law).

1 See, for example, the Wikipedia article on the holographic principle.

2 Siphoning (nice word) the energy "away" would, in turn, use more energy, just like your fridge or your CPU cooler. The colder you want the object, the more energy you need to stem the natural flow of entropy. On a stellar scale you probably need a stellar energy source (something like a death star 2.0 turned beer cooler). That energy source / working star would better be far away because actually you seem to want it cool, locally. So you would need a massive energy conduit from a working star to your (very) dark star, and then the heat pipe going "away".

• My thoughts exactly. It could appear to be endothermic as long as something is siphoning off the energy to a different location. – Thane Brimhall Mar 30 '17 at 22:11
• At first I thought you were being a bit overbearing with entropy. But for a body to continually absorb energy, it would have to remain 'colder' than everything around it, even as it absorbed energy. That energy has to go someplace, or it warms the body. – Xalorous Mar 31 '17 at 3:35
• In a more prosaic context, this is exactly why you cannot have a single-unit cooler (i.e. the reverse of a heater). The best you can have is a heat-pump with a cold end and a hot end, which is why A.C. units have two parts. – Oscar Bravo Mar 31 '17 at 6:27
• @OscarBravo I was thinking about this -- I think you still need a hot end even for your heater ... that is, heating something beyond equilibrium temperature is decreasing local entropy (I think) and needs a process (e.g. generator, electric energy transfer) which increases temperature elsewhere, in addition to the actual heat generated where you want it. You increase entropy elsewhere more than you decrease it locally. That is less obvious when you just burn something because the chemical energy was created by processes long ago, with sunlight, so the system to consider is huge. – Peter - Reinstate Monica Mar 31 '17 at 8:08
• @OscarBravo Actually, another thought: You can have a single-unit cooler, i.e. "create cold" without heat elsewhere at the same time: Certain chemicals, like salts dissolving in water, become cool. This uses chemical energy stored in the separated compounds, much like a candle. The excess entropy is temporally and spatially separated from the use. – Peter - Reinstate Monica Mar 31 '17 at 8:12

In the Electric Universe Theory/Hoax stars are "sumps" that soak up all the cosmic electricity around them. I think the idea is that a star's electromagnetic field is the source of gravity, and the star "burns" because the flow of ions is concentrated there. The electricity comes from outside the star, and the visible star is just an artifact of this electrical phenomena.

I've read a few articles that discuss this concept, or rather, I tried. The logic is often circular, and the whole concept is probably magic dressed up as pseudo-science. Here (or here) is a heady article with I think explains the concept in detail.

• Your link appears to be dead. – kingledion Mar 30 '17 at 1:09
• @kingledion Seems to be working fine for me, but I added an extra copy to the Internet Archive no less. – a CVn Mar 31 '17 at 7:56

A normal star emits "warm radiation" which adds energy to anything that absorbs the radiation. What you seem to want is a source of "cold radiation" which subtracts energy from anything that absorbs it.

Something like this doesn't exist in physics. Well, there is laser cooling, but that only works on individual atoms under lab conditions.

So you would need to make up some form of fictional electromagnetic anti-radiation which is emitted by some kind of equally fictional exotic matter which the star consists of.

I think if the author were to have his characters declare that the body cannot be truly endothermic due to the second law, it would be a great starting point to having them look for where the energy is going. Finding out where could be a great quest for an entire series.

You could pick various of the answers here and use a separate story to explore what that answer predicts would be the 'trick' that would allow the phenomenon to appear as a perfect endothermic body. Then have your heroes prove that that trick doesn't exist.

And you could pick your favorite and have them find the secret in the last episode. Irony would have it turn out to be something of a hoax (Miniature storage cells with massive capacity being charged up to power the RV of a cute EBE family.)

• While this is a worthwhile path that a story could take, if one wants to focus on the endothermic star, I don't think it is actually an answer to the question as asked, and have flagged it for review. – a CVn Mar 31 '17 at 7:57
• Xalorous you make an interesting point/scenario but as the others mentioned it doesn't really address the question being asked. This would be a good note at the bottom of an answer addressing the question that was asked. – James Mar 31 '17 at 12:35