Download Stars and Star Patterns

Stars and Star Patterns
Revised by Tracy Sikes
What is a star?
A star is a huge ball of very hot gases
like hydrogen and helium.
Our sun is the closest star to our
planet.
Stars give off light and heat
energy.
Facts about the sun:
• The center of our solar system.
• Sometimes has dark spots called sun spots
which do not give off as much heat or light.
• Red streams and loops are
called solar flares.
• Both last only a few days.
Scientist classify stars in several
ways:
• By color
• By brightness
• By size
Star Colors: color tells the
temperature
•
•
•
•
Red (coolest)
Yellow
White
Blue (hottest)
Star Brightness
Brightness depends on two things:
• How far it is from Earth.
• How bright it actually is.
Star Sizes
• Stars come in different sizes.
• Some stars are even smaller than Earth.
• The smallest stars are called neutron stars.
What is our Sun?
•
•
•
•
A yellow star
Medium size
Medium brightness
Medium heat
Stars go through stages:
First Stage:
•
•
•
•
•
Stars form as clouds of swirling dust.
Gravity squeezes the cloud.
It circles faster and faster.
The cloud is called a nebula.
A star is born!
What happens next?
• Small stars grow to a Red Giant.
• This star will die and become a White
Dwarf.
What about other stars?
• Big stars explode and are called Super
Novas.
• Some Super Giant stars explode and make a
black hole.
• Nothing can escape a
black hole’s suction
because of gravity.
What about our Sun?
Our sun will grow to be a Red Giant and then
a White Dwarf.
A pattern or
group of stars in
the sky is called
a constellation.
There are 88
constellations in
all.
People of ancient
time saw the
constellations as
characters 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 bothered
the gods.
When the gods
were tired of
him, they sent
a scorpion to
bite and kill
him.
The gods felt
bad for having
Orion killed.
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. Instead it has what is known as the
Southern Cross.
 The Southern Cross consists of 4 bright stars and
some dimmer ones. All of these together point to the
south pole.
What is the Zodiac?
• A group of 12 constellations.
• Lined up one after another all around the
sky.
• Each month a different member of the
Zodiac rises in the east.
• Each day more of it becomes
visible.
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.
What is a galaxy?
• Have you seen a bright band of stars on a
clear summer night?
• That’s the Milky Way Galaxy.
• A galaxy is a huge system
of gasses, dust, and stars.
Billions of stars!
• Our Sun is on the edge of
the Milky Way Galaxy.
Are there different kinds of
galaxies?
Galaxies are generally classified by their
shapes:
• Spiral galaxy- The Milky Way is spiral
• Elliptical galaxy
• Irregular
What is the Universe?
• The universe is everything that exists in
space!
• There are millions of galaxies in the
universe.
•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.
More Review Questions
•
•
•
•
•
How many galaxies are there?
How do scientists classify stars?
What is the name of our galaxy?
What type of galaxy is it?
Describe our star, the sun.