[MUSIC]

Joan Cartan-Hansen, Host: Our
sun is a medium-sized, middle

aged yellow dwarf star.

Stars are huge, glowing balls of
mostly burning hydrogen gas.

They vary in size, temperature,
color and brightness.

The color of a star depends upon
its temperature.

Cooler stars appear red and
hotter stars glow bluer.

Stars begin life in clouds of
hydrogen and dust.

Material clump together, packing
tighter and tighter and hotter

and hotter.

Eventually, the star begins to
burn brightly.

Stars like our sun live for
billions of years.

Our star is about four billion
years old and has enough fuel

for approximately five to eight
billion more.

Stars do eventually die.

Some turn into black holes.

Others collapse and explode.

Becoming a supernova.

The brightest star in our night
sky is Sirius.

It's 8.6 light years away.

That means the light from Sirius
has been traveling for 8 point 6

years.

So, when you look at the stars
at night, you're looking into

the past.

For more information about
astronomy, check out the science

trek website.

You'll find it at science trek
dot org