one day the last star will die and the
universe will turn dark forever
it will probably be a red dwarf a tiny
kind of star that's also one of our best
bets to find alien life and might be the
last home of humanity before the
universe becomes uninhabitable
so what do we know about them and why
are they our last hope
at least 70 percent of stars in the
universe are red dwarfs they are the
tiniest stars out there with only about
seven to fifty percent of the mass of
our sun not that much bigger than our
planet jupiter which is still huge
though
they are also very dim
it's impossible to see them with the
naked eye you've never seen one in the
night sky
even with all our technology we can only
clearly observe red dwarfs in our
neighborhood
approximately 20 of the 30 stars close
to earth are red dwarfs
like all stars red dwarfs fuse hydrogen
into helium
but while more massive stars accumulate
all the fused helium in their cores red
dwarfs stay convective meaning that the
helium and hydrogen constantly mix
so they use up their fuel incredibly
slowly before they're extinguished
red dwarfs burn so slowly that their
average lifespan is between 1 and 10
trillion years
by comparison the sun will survive for
another 5 billion years
because the universe is only 13.75
billion years old not a single red dwarf
has reached later development stages
every single one of the trillions that
exist is still a baby
speaking of babies the smallest star in
the entire universe is also a red dwarf
because small red dwarfs are right on
the verge of being a star at all just a
tiny bit less hydrogen and they are mere
brown dwarfs failed stars that cannot
sustain a fusion reaction for long
so what about aliens or a new home for
humanity
since our sun will die one day we'll
eventually need to look for a new home
and where there are habitable planets
there might also be aliens
the kepler space observatory found that
at least half of all red dwarfs host
rock planets between half and four times
the mass of our earth
many of them are in the habitable zone
the area around a star where water can
be liquid
but since red dwarves burn at relatively
cold temperatures a planet would need to
be really close to be hospitable
probably as close as mercury to our sun
or even closer
which brings with it all kinds of
problems
for example a planet this close to a
star would probably be tidally locked
meaning the same side would always face
it
this side would be incredibly hot while
the shadow side would be frozen which
makes it hard for life to develop
although a planet with a big enough
ocean might be able to distribute the
star's energy and create some kind of
stability
all the gravitational forces of the red
dwarf could squeeze the planet and heat
it up so much that it might lose all its
water over time
these planets could end up like venus a
hot burning hell
another problem is that many red dwarves
vary in their energy output they can be
covered in star spots that condemn their
emitted light by up to 40 percent for
months which would cause oceans on
planets to freeze over at other times
they can emit powerful solar flares
sudden outbursts of energy incredibly
powerful
these red dwarves can double their
brightness in minutes which could strip
away sizeable portions of a planet's
atmosphere and burn it rendering it
sterile
on the other hand their extremely long
lifespan is a big plus
a red dwarf with just moderate levels of
activity could be an amazing place for a
planet that hosts life
life on earth has existed for about four
billion years and we have about a
billion years left before the sun
becomes so hot the complex life on earth
will become impossible we will either
die out or leave earth and look for a
new home
we could build a civilization for
potentially trillions of years around a
red dwarf with the right conditions
about five percent of the red dwarfs in
the milky way may host habitable roughly
earth-sized planets that would be more
than four billion in total
but life may not even need a planet-like
earth
candidates for life around a red dwarf
maybe the moons of gas giants also
called super earths really massive rocky
planets
all in all there are an estimated 60
billion potentially habitable planets
around red dwarfs and that's in the
milky way alone
so red dwarfs might become really
important for our survival in the future
but everything has to die at some point
even red dwarfs
when in trillions of years the life of
the last red dwarf in the universe is
about to end it will not be a very
spectacular event as its hydrogen runs
out it shrinks becoming a blue dwarf
burning out completely
after its fuel is spent it's transformed
into a white dwarf an object about as
small as earth packed very densely and
made of degenerate gases mostly of
helium-4 nuclei
having no more source of energy it will
cool extremely slowly over trillions of
years until it becomes its final form a
cold black dwarf
white and black dwarfs are so
fascinating that they deserve their own
video
anyway it's going to be a long time
before the last stars in the universe
vanish it's kind of uplifting to know
that if humanity succeeds in venturing
into space we have plenty of time before
the universe turns out the lights
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