Mission Control initiate countdown.  Three,
two, one, blast-off!  Hey Isaac here! Welcome
to today's video - the life of a star.  This
video was brought to you by tinfoil hats,
protecting brains since 1970.
Okay wait
before we get going
I want to take off this hat, this tinfoil
hat.  Okay so we are talking about the
life of a star and it all begins in the
nursery.  Rock-a-bye baby, on the treetop.
It begins in what is known as the
stellar nebula.  Stellar nebula...
nebula... nebula... Okay I don't have a sound
effects guy.  So we're gonna use socks to
represent the stellar nebula.  Okay so a
stellar nebula is this place out in
space that has gases and dust and
particles and all sorts of stuff that
forms this great big cloud.  And this is
the birthplace of the star.  Now you may
remember that thing called gravity.  I
hope so!  Did you drop your cereal bowl on
the floor this morning?  That was gravity
that made your bowl fall onto the floor,
break, and spill soggy Cheerios all over
the floor.  That is gravity.  It's a force
that pulls things toward its center.  And
as you may remember, the larger or
heavier an object is, the more gravity it
has.  So the earth has a small gravity,
the moon has an even smaller amount of
gravity, and the Sun has a ginormous
amount of gravity.  Okay, so this gravity,
this force is acting on this pile of
socks or on the gas and dust particles
in the universe.  So this gravity of force -
this force of gravity is pulling these
socks in together and it's packing them
tighter and tighter. I'm gonna use a
plastic bag.  So here we go, I am using
gravity and collecting dust and gas
(mostly hydrogen) into my new forming star
and I'm gonna zip it up and I have a
new star.  Now there are two types of
stars that we'll be talking about today -
the average star which is this, which is
like our Sun.  Okay and then we have a
massive star which is much bigger.  So we
are going to... we are going to pack it.
Remember it's gravity packing this bag
full of socks.  So here we go and we have
this bag or this new star that's made up
of mostly hydrogen with some other small
elements, and molecules, and dust, and
such.  So here we have these two types of
stars - a massive and an average star. Now
right now they're not burning - or they're
not creating energy.  All they are are
hunks of rock and and they're just
these round balls of gas and material,
right?  They haven't started doing
anything yet.  But wait!  This is what we
call a protostar before it it has begun
its life.  Okay now the first breath of
life of a star comes when the gravity is
pulling so hard and it packs it so tight
that something amazing happens.  Something
so incredible.  Because it creates an
enormous amount of energy. 
 I'm gonna use these two balls to
help me illustrate.
So in these new stars you have a
ginormous amount of hydrogen, right?  So
we're gonna use this red ball as
hydrogen and this red ball as hydrogen.
And we are going to - or rather the Sun or
the stars are doing something called
fusion.  they are taking two elements like
two hydrogen in this case and they're
gonna squeeze them together into one
element, okay?  Which is a heavier element
called helium.  You may remember the song
by They Might Be Giants "The Sun is a
mass of incandescent gas a gigantic
nuclear furnace!  Where hydrogen is turned
into helium at a temperature of millions
of degrees."  So that is called fusion.  It
is fusing two atoms of hydrogen together
to make one helium.  So watch!  Now one
thing I need to mention before I do this
really cool magic trick.  These hydrogen -
they required - they they're like
neighbors that hate each other.  They do
not want to get together.  So it takes an
enormous amount of temperature in order
to get that to happen.  And that's what
happens with gravity.  It gets to a point
where it's sucking in so hard and it
creates... it's so dense and packed.  And as
it gets packed and more dense it gets
hotter and hotter and hotter and it gets
to a point where it's hot enough to turn
these two hydrogen into helium.  So watch. 
Here we go hydrogen.  We're getting hotter,
we're getting hotter, we're getting
packed.
And we have a helium!
I know cool right?  Now in the process of
turning those two hydrogen into this one
helium, there is released an enormous
amount of energy and light.  And that is
what reaches our Earth from the Sun.  Our
Sun, which is an average star, is
converting millions and billions of
atoms of hydrogen.  It is converting them
into helium by squishing them together
and that's what powers the Sun.  And
that's what the lifecycle of a star is -
or the life is - they will spend a certain
amount of time squishing, and squishing,
and squishing.  Converting hydrogen into
helium and giving off all this in
light.  But there comes an end to that
right?  Just like your car when you're on
your way to your favorite fast-food
restaurant and your dad forgot to look
at the gas gauge.  Everything runs out of
gas.  So do these stars.  They will run out
of gas too and when they run out of gas
something happens.  If you are an average
star and you run out of gas, what happens
is, hmm, relatively speaking a fairly
peaceful process.  This star eventually
shrinks - well it'll grow to become a red
giant - but then it runs out of gas and
shrinks, and shrinks, and shrinks, until it
becomes a white dwarf And eventually
all those elements and everything in that
star are just gonna cool and it's just
gonna be one big hunk of rock star. Not
creating any more energy.  That's a white
dwarf but something amazing happens when
you get to these larger stars, these
massive stars.  Because remember that
gravity is so great and so strong that
when these guys run out of energy
something amazing happens that you may
have heard in a song or on the
television.  It's called a
SUPERNOVA!!!
Now a supernova
is when a massive star runs out of gas
and explodes and sends material all over
the universe.  Now once that star has
exploded a couple of things can happen.
First
the remaining core which, will be much
smaller and even smaller than these -
than these other stars, it will form
what's called a neutron star.  A star made
out of neutrons!  It is totally evaporated
and destroyed electrons and protons.  But
something even more amazing happens to
the larger mass of stars.  They make
something called - are you ready?  Can you
handle this?  A black hole!  A black hole,
that's where it comes from.  A massive
star that went KABOOM and then the
gravity shrunk the
remaining material and mass into a hole.
It's not really a hole but it's a place
that has so great density in such a
small place that the gravity is enormous.
And this gravity being so enormous is so
strong that it will suck in things
around it.  Like other planets, other stars,
other asteroids, other toilets floating around in
space! I don't know why they're floating
in space, but they are.  And even light.
that's why they're called a black hole
because the gravity is so strong it
won't even let light escape.  And one more
thing I want to mention about these
massive stars when they explode. Because
as these massive stars - you're just gonna
have to remember because I exploded my
sock bag - these massive stars.  Within them,
when they start to run out of gas, right
they got hydrogen turning into helium.
Well eventually they're gonna - they
become so hot it'll turn helium, and
larger atoms, and larger atoms, all the
way up to lead.  Okay so in these
massive stars, you're making things as
big as lead right out of smaller atoms.
But when you go supernova, it becomes so
hot then it makes the heavier elements
like gold and silver and copper.  Those
things come directly from a supernova.
Amazing huh?
So that is the life cycle of star.  The
birth, the life, and the glorious death
of something amazing.  Now our star is
only expected to live around ten billion years and it's estimated
that it's around five billion years old.
So someday our star may run out of
energy too but you shouldn't worry about
that unless you live to be billions of
years old.  So that is the life cycle of a
star and I hope to see you outside
sometime, looking at all those amazing
stars and enjoying the beauty of nature.
This is Isaac Ashby. 
We'll see you outside.
Find more STEAM lessons, activities and experiments just like this
in our STEAM Outside homeschool program at STEAMOutside.com.
