Given that the universe has exited its prime star formation phase and that fewer sun-like stars will be birthed in the future, will there come a time before the universal heat death that life cannot exist because only red dwarf stars will remain in the far future?
I think you are begging the question a bit with the idea that life would be impossible if there were only red dwarfs.
Yes, in about 1 trillion years, the only stars in the universe still fusing hydrogen will be red dwarfs. But I don’t know that it follows that this makes life impossible.
Is this accurate?
I regularly see recent astronomical pictures of the sky, with the captions pointing out areas as ‘star forming regions’. Areas where gravity, galaxy collisions (near passes), etc. are pulling interstellar dust or other mass objects together, eventually becoming massive enough to form into a star and begin fusing.
Is this something that happened long ago that we are just seeing now? Because I’m not sure I see any reason for this process to stop.
Cosmic Noon, when star formation was 10 to 30 times faster than today, happened 10 billion years ago. Today star formation is merely 3 percent of what it was during peak star formation 10 billion years ago. Stars still form, but at a much lower rate.
Its possible according to this paper that life genesis will be at its peak 1-10 trillion years from now when the universe is red dwarfs. Since red dwarfs are much more stable than stars like ours they give more time for life to emerge.
https://arxiv.org/pdf/1606.08448
Here on earth our sun limits when life can evolve, especially on land. In a billion years life on land won’t be possible because the sun will be too bright. Red Dwarfs are far more stable, offering longer timelines for life to evolve on planets.
I’ve mentioned this before, and I’ll mention it again; red dwarfs get brighter over time, because the hydrogen turns to helium, and this makes the star denser and brighter. A trillion years from now, many or most red dwarfs will be approximately as bright as the Sun is now, so I’d expect the surface brightness and habitability of the galaxy to be much greater in that era.
The galaxy might be full of life in the distant future; on the other hand even this distant heyday could not last forever, and all the stars will be dead a quadrillion years from now.
I don’t recall where I recently read about an experiment to see how well photosynthesis works under the light from a red giant. It works well and that is the photosynthesis that evolved under our sun.
What is likely to happen as the universe winds down is not that life is impossible, but it would likely take place at a much slower speed and a much larger scale. Conversely, you can speculate that during the first three minutes after the big bang that life formed, evolved, went extinct all at vastly high speed and tiny tiny scale.
The universe is a big place. Even now, there may be lifeforms which don’t depend on a nearby star at all. Even humanity may reach a stage of technological development where everyone is living comfily on space stations which generate their own heat, light and power.
Rogue planets, worlds that drift through interstellar space without a parent star could potentially support life, though not on their surfaces.
How long could a self contained space station continue to generate power and through what means?
You all seem to be assuming that the expansion of the universe will continue, or possibly accelerate, in the future, leading to the so called “heat death” of the universe. But we know that dark energy hasn’t been constant. There’s no reason to believe that at some point in the future that dark energy won’t become weaker or even become an attractive force, at which time the heat death hypothesis won’t necessarily be the obvious future of the universe.
We only know that in the sense that it hasn’t remained inflationary. Cosmic inflation might have been the same phenomenon as modern dark energy, just (for some reason) now diminished by googolian proportions, or they might be two completely different phenomena, qualitatively (but very much not quantitatively) similar in their effects, but with different durations.
But yes, given what we know, and more importantly given what we don’t know, it’s entirely possible that the dark energy will diminish or even reverse. Or of course that it might strengthen. Heat death is the simplest hypothesis, but it’s not the only one.
Just as I could not have predicted the internal combustion engine and nuclear power 300 years ago, who knows what energy sources might be developed 300 - or 3,000, or 3,000,000 - years from now?
It’s worth separating out the prospect of life starting near a red dwarf, and life making use of them at some future time.
Even if red dwarfs are unsuitable for life (and we don’t know this) because of tidal locking, powerful flares etc, it wouldn’t entail that a universe of only red dwarfs would be sterile.
I believe you can actually get an incredible amount of energy by dropping stuff into a black hole.
I would like to thank you for the correct usage of “begging the question”.
Space stations (including large habitable megastructures) should not be considered as closed systems for the purposes of energy use. Many or most space habitats would be located relatively near a source of energy, perhaps a star, a brown dwarf, a gas giant emitting radiative energy and magnetic energy, or even an exotic object such as a black hole or pulsar. Any of these objects could be used to provide energy for a habitat, directly or indirectly.
Even a habitat far from any star could recieve energy from a collection system near such a source of energy; only one billionth of the Sun’s energy falls on a habitable planet - some or most of the rest could be collected and collimated to supply a billion more Earth-sized habitable surfaces at arbitrary distances from the star itself.
And given hydrogen fusion as an energy source, then the various icy objects of every Oort cloud could support life until the fusable elements are exhausted - this option has limits that might reduce its usefulness in the very long run, but at least it allows a certain amount of independence.
This is true (up to half of the amount you could get through total conversion to energy), but I think that it misses the real prize. You can also use a black hole to make your usage of the energy you have much more efficient. To convert heat into useful forms of energy, you need to have a temperature difference, and the efficiency depends on the ratio of the temperatures. But black holes (at least, ones of a reasonable size) are far, far colder than anything else in the Universe, so by using one as your cold sink, you could get near-total efficiency out of reusing heat even at a few hundred kelvins (like the waste heat that human bodies produce). And unlike normal heat sinks, which increase their temperature (and so eventually become useless) when you put energy into them, black holes actually decrease their temperature when you add energy to them.
And the spin energy of the black hole could be extracted by various means, a process which would actually decrease the mass-energy of the hole. Eventually, though, the hole would stop spinning.
This is true, but if we are talking about a civilization that consumes the Earth’s annual energy budget in a year (the Earth, not humanity - so all the energy that the Earth absorbs from the sun in one year) in one day, then it would take them trillions of years to deplete the rotational energy of a supermassive black hole.
And if they were consuming that much total energy each day, as @Chronos notes, their efficiency would allow them to do orders of magnitude more with it than we would. So we are talking about a truly mind numbingly colossal amount of energy.
Invest in real estate property around Sagittarius A* and you’ll be thanking me in a few trillion years when every Kardaschev Type III Civilization comes knocking to buy it off your hands.
Most black holes are stellar mass black holes, and contain much less mass than a SMBH; but even with these objects there is plenty of spin energy, Quiet, solitary black holes are probably quite numerous - there are many we can’t see, because they are black, and, you know, the basic colour of space is black. But eventually the SMBHs will be the best real estate, as you say.
Curiously the gravity around such a large black hole would be sufficient to slow down time for an object in orbit around it - so you could use it as a one-way tardis into the future, past the red dwarf era (which, as I should mention once again, might be the era of peak habitability).