Finding the North Star

JAMES: Welcome to Star Gazers.

I'm James Albury, director of the Kika Silva
Pla Planetarium in Gainesville, Florida.

DEAN: And I'm Dean Regas, astronomer from
the Cincinnati Observatory, and we're here

to help you find you way around the sky.

JAMES: If someone asked you right now to name
the brightest star we can see in the sky what

would you say?

DEAN: The Sun!

JAMES: That s true.

You re going to be technical today, aren t
you?

Buuuuut what about the brightest star you
can see in the nighttime sky?

DEAN: If you re thinking of Sirius out there
folks, you're right.

But if you said the North Star you're not
so right.

But don't feel bad if you said the North Star,
because most people believe that the North

Star is the brightest star, when in fact there
are about 50 other stars visible to the naked

eye which are brighter.

So why do so many people think the North Star
is the brightest star?

JAMES: Well, one reason might be that so many
people have heard so much about the North

Star that they assume it must be the brightest,
when in fact it is really the most important

star, at least as far as sailing the seas,
flying a plane or traveling from place to

place.

Let's show you.

JAMES: O.K., we've got our skies set up so
that we're facing due north any night this

week around 9:30 p.m.,
where you should easily be able to find the

Big Dipper.

Those 4 stars that make its cup and the 3
stars that make its handle are so distinct

in the spring sky.

DEAN: And if you want to find the North
Star for yourself, all you have to do is use

the two stars at the end of the cup, which
are appropriately called, the pointer stars.

All the boy scouts and girl scouts in the
audience know this trick already, but when

you shoot an arrow through
them and continue that line down and to the

left the pointer stars will always point you
to the North Star.

JAMES: Now once you've found it, you'll notice
the North Star is about the same brightness

as the pointer stars.

So since the North Star doesn t stand out,
why is it so important?

JAMES: Well I'll give you a clue: the North
Star is also called Polaris because it is

the closest bright star to the north celestial
pole.

DEAN: So what? (you may be asking)

JAMES: Welllll, this simply means that if
we could stand at the north pole, the North

Star, Polaris, would be directly overhead,
which further means that it is directly above

the Earth's axis.

DEAN: Now if you think of the Earth's axis
as a huge nail we could insert it at the south

pole and it would go all the way through the
Earth and come out the north pole and extend

out into space; that nail, the Earth's axis,
would point to the North Star.

JAMES: So what? (you may be asking)

DEAN: Wellllll, This also means that as the
Earth turns on its axis, all the stars in

the heavens would seem to move except one...The
star directly above the Earth's axis, Polaris

the North Star.

That's why Polaris, the North Star is so important.

JAMES: You see, Polaris is the only star which
remains stationary in the heavens while all

the other stars slowly circle around it.

It is always due north, so before the invention
of the compass, this star was extremely important

to navigators and explorers to determine direction.

DEAN: In fact, if you're lost at night and
don't know which direction you're headed,

simply find the Big Dipper, then use the pointer
stars to find the North Star and for as long

as you live, the North Star will always be
due north.

And if it's not, you're either on a different
planet, like Mars

whose North Star is Deneb, the tail of Cygnus
the Swan....

JAMES: Or you could be on Earth, but in a
different century.

You see, Polaris won't always be our North
Star.

The Earth's axis slowly wobbles in a motion
we call precession.

This slow wobble takes about 26,000 years
to complete, moving 1 degree every 72 years.

So, 3000 years ago, Polaris wasn't considered
the pole star.

And in 14,000 years, the bright star Vega,
in Lyra the Harp, will be our pole star.

DEAN: Hmmm

I guess in 14,000 years Polaris won t be
the North Star and will have to change its

name.

Until then

BOTH: Keep looking up!