Transcript Constellations Powerpoint

Constellations
A pattern or
group of stars in
the sky is called
a constellation.
People of ancient
time saw the
constellations as
character or
animals in the sky.
They made up
stories to explain
how the object,
animal, or character
came into the night
sky.
Orion
Orion is one
of the
brightest
constellations
and is a
mythological
character.
According to
Greek myths,
Orion was a
hunter who
used to brag
all the time.
This bother
the gods.
When the gods
were tired of
him, the sent a
scorpion to
bite and kill
him.
The gods felt
bad for doing
having Orion
killed, they
they placed
him in the sky.
Stars as Tools for Navigation
 Earth rotates on its axis, this makes most
constellations appear to rise in the east and set in the
west during the night.
 Most constellations appear in many different positions
in the sky as the Earth revolves around the sun.
 There is a group of stars that appear in the sky all
night long and all year long. It seems that these stars do
not rise and set, but circle the Earth’s north pole each
night. These stars are called circumpolar.
Stars as Tools for Navigation
 The North Star is called Polaris and located directly
above the North Pole. This star appears in the same place
every night all year long.
 In the Northern Hemisphere, if you find Polaris you
will be able to tell which direction is north.
The Southern Hemisphere does not have a star to help
you find its pole. In stead it has what is known as a
Southern Cross.
 The Southern Cross consists of 4 bright stars and
some dimmer ones. All of these together point to the
south pole.
Stars As Calendars
 It seems that the constellations in the east rise a little
earlier each evening. This means that the seasons are
changing and we are seeing different constellations.
 An example is in the Northern Hemisphere, Orion is
high in the sky during the winter and Scorpio can only
be seen during the summer.
 People of ancient times used these seasonal changes
in the stars as calendars.
 It is believed that the ancient people used the
constellations to tell them when to plant and harvest
crops. An example would be Leo and Virgo in the
night sky would signify that the last frosts of the year
have happened and it is safe to plant. This worked
much like our paper calendars work for us today.
The brightest constellation is Crux (the Southern Cross).
The constellation with the greatest number of visible stars
in it is Centaurus (the Centaur - with 101 stars). The
largest constellation is Hydra (The Water Snake) which
extends over 3.158% of the sky.
1. What is a constellation?
2. Why is Polaris called the North Star?
3. How did ancient people use the seasonal
appearance of certain constellations?
4. Name two constellations.