- 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 thousands 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]