Stars and Star Patterns

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Stars and Star Patterns Revised by Tracy Sikes
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What is a star?

• A star is a huge ball of very hot gases like
  hydrogen and helium.

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Our sun is the closest star to our planet.
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Stars give off light and heat energy.
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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.

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Scientist classify stars in several ways

• By color
• By brightness
• By size

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Star Colors color tells the temperature

• Red (coolest)
• Yellow
• White
• Blue (hottest)

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Star Brightness

• Brightness depends on two things
• How far it is from Earth.
• How bright it actually is.

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Star Sizes

• Stars come in different sizes.
• Some stars are even smaller than Earth.
• The smallest stars are called neutron stars.

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What is our Sun?

• A yellow star
• Medium size
• Medium brightness
• Medium heat

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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!

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• What happens next?
• Small stars grow to a Red Giant.
• This star will die and become a White Dwarf.

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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 holes suction
• because of gravity.

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What about our Sun?

• Our sun will grow to be a Red Giant and then a
  White Dwarf.

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Patterns of Stars
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.
A pattern or group of stars in the sky is called
a constellation. There are 88 constellations in
all.
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Orion
When the gods were tired of him, they sent a
scorpion to bite and kill him.
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.
The gods felt bad for having Orion killed. They
placed him in the sky.
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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
  Earths north pole each night. These stars are
  called circumpolar.

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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.

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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.

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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.

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What is a galaxy?

• Have you seen a bright band of stars on a clear
  summer night?
• Thats 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.

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Are there different kinds of galaxies?

• Galaxies are generally classified by their
  shapes
• Spiral galaxy- The Milky Way is spiral
• Elliptical galaxy
• Irregular

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What is the Universe?

• The universe is everything that exists in space!
• There are millions of galaxies in the universe.

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Interesting Facts

• 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.

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Quick Review
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.
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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.