Locating the Pole Star Video Lecture - Class 8

well tonight it's a lovely clear night
and I'm gonna be showing you how to find
the pole star Polaris as a really useful
navigation tool at night because if
you're in the northern hemisphere it
always points north and to find it we're
going to have to look for one of the
most recognizable patterns of stars in
the sky called the Big Dipper or the
plough and it's part of the Ursa Major
or Great Bear constellation the plough
or Big Dipper
is made up of seven quite bright stars
in the form of a saucepan or a ladle
although if you look closely the second
star from the left Mizar has a fainter
companion I'll call what you need to do
is find the two stars at the end of the
bowl mirac and do be these act as
pointer stars for the pole star follow
the line in the direction shown if we
zoom out you can now see the plough or
Big Dipper at the bottom and the N two
pointer stars now we can see if you
follow the line for about five times the
distance between mirac and Dubey you'll
reach a fairly bright star this is the
pole star or Polaris now some people
expect the pole star to be the brightest
star in the sky it's not it's about the
fiftieth brightest that actually does
rise and fall in brightness in a regular
way it's a variable star it's actually
about 25 times fainter from the
brightest star Sirius it is however the
only reasonably bright star in that area
so it's quite easy to know that you've
got the right one
now the Polestar doesn't move very much
because it is almost directly above the
Earth's North Pole and so as the Earth
rotates underneath it you're hardly
appears to move and it's this fact that
means we can use it because it nearly
always points north but also we can use
it to measure our latitude on the earth
so for instance right here in the UK I'm
at about 53 degrees north and so that
means that Polaris is 53 degrees in
angle in altitude above the horizon so
we can measure how high above the
horizon priorities you can work out your
latitude and this was extremely useful
for early Mariners so there you have it
that is how to find the pole star so
hopefully see you again soon
see again
you