- Did you know that when you
look up in the dark night sky,
you are, in a way,
looking back in time?
It's really true.
Much of the light you see
coming from the stars
has been travelling across
space for millions of years
by the time it reaches us
here on Earth.
Some of those stars that you can
see tonight in the night sky
may have burned out
millions of years ago.
If you have ever wondered
where stars come from,
how they change,
and what happens to them
when their life
comes to an end,
hang with me for a few minutes
as this episode
of "NASA Launchpad"
takes a closer look
at the life cycle of stars,
and bonus, we are going to talk
a little bit about how
each of us is actually
made from dead stars.
Yeah, really.
[upbeat electronic music]
- Lift off.
[upbeat electronic music]
- Most things in the universe
have a life cycle.
Thankfully for some things,
like these guys,
the life cycle
is incredibly short.
But for other things,
like stars,
the life cycle
can be billions of years long.
The life cycles for stars begin
in giant stellar nurseries
called nebula.
If you look at one of these
star-forming nebula,
you will see beautiful
giant clouds of dust and gas.
How a star forms
is a little technical,
so let's hear an explanation
from an expert.
- A star is basically
a nuclear furnace.
It's this collection of
mostly hydrogen gas,
and at the center it's really,
really hot and dense,
where you can actually get
nuclear fusion occurring,
and that's how you get the heat
and the light from the star.
In space you have this
collection of sort of
diffused gas and dust particles.
It's just sort of everywhere
in space.
Occasionally it comes
together through gravity.
It's attracted to itself
basically,
and so you get these
giant molecular clouds
that are called
these big nebula.
As that stuff comes together
through its own gravity,
you eventually get these places
where you have enough material
where you can start
to form a star,
where it all comes together
and the gravity pushes on it
so hard that it heats up
in the center,
and that heating up
is what will eventually lead to
fusion and the birth of a star.
Two of the most important
properties of a star
are its color
and its brightness.
And so if you take stars and
you sort of sort them by color,
you get anything from
red to blue,
where the red stars
will be the cooler stars
and the blue stars
will be the hotter stars,
so that's really
a measure of temperature.
And then you can also sort them
by their brightness,
and so you have
the very bright stars,
which are usually
the more massive stars,
and the dimmer stars,
which are usually less massive.
And just by
these two parameters,
you can actually tell a lot
from a star.
You can tell how massive it is.
You can tell how big it is,
its radius.
You can tell how old it is.
You can know what stage
of evolution it's in,
and you can learn about
the environment of the star--
that the star was born in.
- As you know,
our sun is a star.
It is actually
a fairly modest sized star.
It is believed that our sun
is about halfway through
its 10-billion-year life cycle.
Yes, that makes our sun about
5 billion years old.
But don't worry.
We're all good for at least
another 5 billion more years.
So how will our sun's life cycle
play out?
- So our sun is a low mass star,
and it's actually gonna go
through a really long evolution.
It's going to be in the phase
that it's currently in,
where it's just fusing hydrogen
into helium,
for about 10 billion years.
And then once it runs out
of fuel in its center,
it's going to evolve into
a red giant star,
red meaning
that it's gonna be cooler,
and it's gonna be so large
that its outer radius
is actually gonna reach
the Earth's orbit.
It's gonna be a huge star.
And then eventually
it'll blow off its outer layers
and become a white dwarf star,
and that will be the--
its final phase.
- So at the end
of a massive star's life,
we have what's called
a core collapse super nova.
So the core region collapses
in on itself
and the outer region infalls
and then rebounds,
and you get left with
a neutron star or a black hole.
- You have may have noticed that
no matter the size of the star,
at the end of its life cycle,
most of its material
is expelled back into clouds
of dust and gas in the galaxy.
The life cycle of a star
can begin again.
- Throughout a star's life,
it's throwing off material,
and this material
has been enriched
by nuclear fusion reaction,
so originally
really only hydrogen
and a little bit of helium
was produced in the big bang,
and all of the elements
that we get after that
have been produced
in either a star's life
or in its explosion if
it's massive enough to explode.
And that material gets mixed in
with the other gasses and dust
in the interstellar medium,
and produces the next generation
of stars.
So every generation of stars
that you produce
is more and more enriched
with material from the life
and death of stars.
- So what does all of this
mean for us?
And what is our connection
to the cosmos?
- All of that fusion
that's going on in the centers
of stars is creating heavier
and heavier elements,
and that's how you get basically
everything you see around you,
from the carbon to the iron,
the oxygen, everything.
You can't get any of those
elements without having a star
forming it
in the first place.
And so everything that your body
is made up,
everything that you see
around you
all came from the center
of a star.
- Pretty amazing, isn't it?
When you look at
that periodic table
hanging in your science class,
it represents all of the natural
and man-made elements.
Most of those natural elements
were formed and fused
inside of long-dead stars.
Yeah, that's right.
Everything around you,
including you and me,
was formed from the remnants
of exploded stars
and the birth of the universe.
We may look and act
differently from each other,
but we are all made up
of the same stuff.
Want to find out more?
You can learn more about stars
and their life cycles
from these NASA websites.
That's it for now.
See you next time
on "NASA Launchpad."
[upbeat electronic music]
