(JMG) This is part 1 in a two part collaboration with Ohio State University Astrophysicist
Dr. Paul Sutter.
You can find part II on his channel, Ask a Spaceman, link in the endscreen of this video
and in the description below, where I ask him specific questions about some of the universe’s
strangest stars, including the infamous Pryzybylski’s Star that I covered on this channel, which
seems to contain elements heavier than Plutonium which, at least up until recently, were not
thought to exist in nature except under laboratory conditions
The universe is ancient by our standards, about 13.8 billion years old, but in a way
it could still be very young in comparison to how long it might yet be around.
Unfortunately, we don’t know the answer to the question of how long the universe will
live.
If, for example, the universe is a false vacuum not existing at its lowest energy state, it
could, at any time, tunnel to that state which would reconfigure all matter in the universe.
Or, another take is that it could endure for more than trillions of years if the heat death
theory is correct, which is the notion of the universe lasting indefinitely as everything
eventually goes dark and cold.
But none of that is certain.
But if it does endure for immense amounts of time, it will grow increasingly strange
as it ages and new types of stars will begin to appear that do not yet exist because the
universe just simply has not been around long enough for them to form.
(over to PS) The universe is currently full of heat and useable energy, and will remain
so for an immense amount of time.
But eventually, that useable energy will reduce as the universe expands and cools its way
towards a temperature of absolute zero.
We often talk about the sun as though its life will end when it reaches the red giant
stage of its life in five billion years.
But this is not the case, life on Earth will surely end from the extreme temperatures,
but the sun will continue to go through other phases of life after the red giant phase,
with the remnant core persisting as a white dwarf.
A white dwarf is essentially a really hot cinder, a stellar remnant holding enough leftover
heat to last for trillions of years, but with no nuclear fusion still occurring.
These stellar remnants already exist, in fact Sirius B, a companion of the brightest star
in the night sky, is a white dwarf only 8.6 light years away.
But what hasn’t yet happened is for a white dwarf to cool so much that it becomes a hypothetical
kind of star called a black dwarf and radiates little to nothing.
In fact, no star in the universe has ever reached this stage.
But what we have found are several cool white dwarfs that are extremely ancient at 11 to
12 billion years that seem to be on their way to this state.
In fact, these stars are one measure in determining the age of the universe.
But it will take many many billions of years for them to cool and go black.
Once that happens, they will be invisible other than their gravitational effects on
other objects.
And some day, the universe will be full of these cinder stars until it too goes black.
(Back to JMG) As an aside, because of their longevity, the radiant energy of a white dwarf
could be harnessed by a civilization as a source of power, even towards the end of the
universe.
In fact, Dyson spheres encasing white dwarfs are thought to be one of the more viable types
of that technology since they would not need to be anywhere near as large as one enclosing
a main sequence star.
With one, a civilization could sustain itself long after most stars have left the main sequence.
Perhaps some day, if we’ve survived the sun’s red giant phase, we might return to
our solar system of origin and once again use the remains of the sun for power.
But it would not be a permanent state of affairs.
As the remnant sun cools to become a black dwarf, the less energy would be available
to us until all that’s left is a very cold cinder and we’d have to move on.
There are still certain questions that we do not know the answers to, such as do protons
eventually decay?
If they do, or if weakly interactive massive particles are found to exist, these exotic
interactions could keep a black dwarf very slightly warm for a longer amount of time
in the distant far future.
But what of stars that live for a very long time as normal hydrogen fusing stars, specifically
the type M red dwarfs that last billions of years?
Will they have a stage in life that no star has yet gone through?
The answer is yes.
Essentially, the universe hasn’t been around long enough for one of these to exhaust its
hydrogen supply.
Here, there is a hypothetical intermediate stage, termed a blue dwarf, where the star
becomes hotter and thus bluer, until eventually it too evolves into a white dwarf, and finally
goes black.
(Over to PS) So far we’ve covered fairly intuitive end game scenarios for stars as
we know them providing that the universe endures for a long period of time.
But there are other possibilities for very far future stars, and they get very strange
in comparison to what we see now.
The first of these is a hypothetical star known as a frozen star.
This type of star is dependent on metal, as the universe ages and more supernovas and
kilonovas occur, the more metal becomes present in the universe.
This changes the rules for stars.
Currently a brown dwarf is something between a planet and a star, many times larger than
Jupiter, but not large enough to start fusing hydrogen.
But with more metals around, stars like this that form in the future might become able
to fuse hydrogen and thus result in extremely cool stars that can’t exist now.
They would be so cool that some of them would have a surface temperature of 0 degrees celsius,
hence frozen.
Compare this to the sun as it is now at over 5500 degrees celsius.
This would lead to an unbelievably dim class of star star complete with water ice clouds.
Some day, these may be among the universe’s most common stars as their hot counterparts
disappear.
(Back to JMG) And now we go to a far future that honestly is hard to comprehend.
For this last type of star to exist, the amount of time you need for it to happen is truly
mind boggling.
Think, as far as years, 10 followed by 1,500 zeros.
This one goes back to to the possibility of proton decay, we don’t yet know if protons
eventually do that.
If they do, this kind of star is off the table.
If they do not, then the situation would then be dependent on the phenomenon of quantum
tunneling.
We know that quantum tunneling exists, despite it being being a very odd, counterintuitive
property of the universe.
In fact, in electronics there is something called a tunnel diode that depends on the
effect that was developed by Sony back in the 1950’s.
It amounts essentially to subatomic particles passing through barriers that they usually
could not.
Most of the time they can’t get past a barrier any more than you can walk through a wall.
But occasionally, they simply do pass through.
And you might pass through a wall as well if you waited long enough for it to happen.
It’s all about probabilities and time.
A way to visualize this is through the particle-wave duality nature of quantum mechanics.
This says that subatomic particles are more like smears on space time than dots floating
around.
Because of that, you can’t really tell exactly where they are at any given time.
The universe simply doesn’t let you.
As a result a particle that’s heading towards a barrier has a probability that it might
actually be located beyond that barrier.
And, sometimes it is, allowing it to seemingly pass through an impassible barrier when in
fact it was all just a matter of probabilities of where it actually was.
This is a can of worms in a universe that could last for an infinite amount of time.
If you wait long enough, entire objects, such as a person could randomly teleport somewhere
else, and even instantaneously cross the universe.
Yes, it’s possible you could wake up on another planet one day, or inside a star.
But, in a universe that does not last an infinite amount of time, this not so much of an issue
since the odds are ridiculous without infinite time for it to happen.
But on a smaller time scale than infinite this effect could allow for the eventual formation
of iron stars.
This would be a star where quantum tunneling would allow fusion to occur ultimately producing
iron.
Eventually, as this process completes, you would be left with a former star converted
into a sphere of iron.
But given the time scales needed to form one of these, it’s beyond unlikely that there
will be anyone left to observe these final remnants of stars.
The available energy in the universe at this time would be so low that anyone left at the
end of the universe as we know it, would have hung up their hats and moved into oblivion.
But these kinds of stars are merely what awaits us in the future as the universe ages.
Currently, there are other types of bizarre stars, many of which I’ve covered on this
channel in the past, some of which I have not.
To explore those, join Paul and I for part two on his channel where I ask an astrophysicist
about specific examples of strange stars and we discuss the possibilities of what else
might be out there.
Thanks for listening!
I am John Michael Godier (to Paul) and I am Dr. Paul M. Sutter and we hope you enjoyed
this collaboration.
(to JMG) and be sure to subscribe to our channels for
regular, in-depth explorations into the worlds of science, astrophysics and the possibilities
of what may await us we explore this amazing universe in which we live.