(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.
