Transcript Stars & Constellations

Stars & Constellations
D. Crowley, 2007
Stars & Constellations
 To know what a star and constellation is
How big is the universe?
 Cut out the pictures, order them, and stick them into your
book…
Person
School
Town
Country
Planet
Solar system
Galaxy
Galaxies
UNIVERSE
Sizes
Sizes
Sizes
Sizes
Sizes
Stars
 What is a star? What is the sun?
 Stars form from clouds of dust, which spiral together due to
gravitational attraction. The gravity compresses the matter so
much that intense heat develops, causing a nuclear fusion
reaction
 Stars emit light and radiation (unlike planets) due to this
nuclear reaction - they are the sources of light!
 But remember - the sun is a star too! It just looks different to
all the other twinkles in the sky, because it is so much closer to
us than any other star!
Stars
 Why is our star (the sun) so big? How far away are other stars?
 Our sun looks much bigger than all the other stars we can see,
but actually its quite ordinary (not the biggest, not the
smallest)
 Our sun is one of many millions of stars which forms the galaxy
The Milky Way
 The distance between stars is usually millions of times greater
than the distance between planets in our solar system - but
remember, these planets are millions of kilometers apart
themselves!
Star Movement
 Why do the stars move across the sky?
 The stars seem to move across the sky because the Earth is
rotating. Just like we see the sun rise and set, the stars seem
to move across the sky as the Earth spins.
How many stars?
 How many stars are there?!
 This is a tough question to answer, as there seem to be lots to
count
 We estimate there are thousands or millions of stars in our
galaxy, the Milky Way
 And don’t forget there are billions of other galaxies…
 That makes for a lot of stars!
Constellations
 What are constellations? Can you name any?
 Constellations are groups of stars which may resemble
something. We make up constellations, so it makes it easier for
us to spot individual stars
 It helps as it breaks the night sky up into manageable bits, so
you may be able to identify a group of stars very quickly and
easily, e.g. The Big Dipper
Constellations
E.g. the Big Dipper;
Orion; Cassiopeia etc…
Using Constellations

How do you think constellations can be useful?

Many would have used the constellations for religious purposes - i.e.
they may have formed a shape which early people took to mean
something

Agriculture has also benefited from constellations - some
constellations are only seen during certain parts of the year - this
helped before proper calendar systems!

Navigation also used constellations, and sometimes still does today.
Some constellations could be spotted, e.g. Ursa Minor contain Polaris,
the North Star (which always points North). Once navigators had
found North, they could observe its height in the sky and hence work
out their latitude (how far North / South they are). Now they know
how far North they are + the direction they’re traveling
Reading the night sky

Have a go at the worksheet, reading the night sky…

Constellations move in the night sky because the Earth is rotating

We see different constellations at different times of the year because
the Earth orbits around the sun

However some constellations can be seen all year round. Some, like
Cassiopeia are circumpolar - this means they circle above the pole, so
can always been seen (the Earth’s orbit around the sun does not
affect their viewing)

Navigation utilises constellations - it helps locate a specific star, such
as Polaris (the North Star). Knowing this, plus how high the star is in
the sky gives a navigator their direction + their latitude (how far
North / South they are)