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How was the universe
created?
•Big
Bang Theory
•An explosion occurred 10-15 billion years
ago in space causing the universe to expand
in all directions
Edwin Hubble
•American
astronomer
•Discovered that other galaxies in the
universe were moving away from
us…which would mean at one time they
were all together at one point
•The Hubble Telescope was named in his
honor
What is the Milky Way?
•A cluster of stars called a galaxy
•Contains hundreds of billions of stars
•Traveling at the speed of light-it would take
about 2 million years to reach another
galaxy…the Andromeda Galaxy
•It’s where our solar system is located
The Milky Way
•Often called “Our Galaxy”
Types of Galaxies
• Spiral
•
•
• Irregular
Elliptical
Spiral Galaxies
•Resembles a pinwheel
•Our solar system is located about 2/3 of the
way out on one of the spiral arms
•It’s difficult to see the spiral shape of our
galaxy because we’re on the inside
Elliptical Galaxies
•Resemble a flattened ball
•Contain billions of stars & little to no dust
between them
•Stars are really close together-may even appear
to be 1 giant star
•Consist of old stars
Irregular Galaxies
•Irregular shape
•Large Magellanic Cloud is about 160,000 light
years away from us
What about the
stars?
•Stars begin as a large cloud of dust & gas
called a nebula
Protostar
•The nebula contracts & becomes so hot
that nuclear fusion begins…causing a
protostar to be born
Red Giant/Supergiant
•A star becomes a red giant or a supergiant
when it begins to run out of fuel
What happens to a dying star?
•When a star begins to “die” it becomes a
white dwarf, a neutron star, or a black
hole
White Dwarf
•Blue-white hot core of a star left behind from a
red giant
•About the size of Earth
•Have no fuel-just burn from leftover energy
•Becomes a black dwarf when it stops glowing
Neutron Star
•Smaller & denser than white dwarfs
•May contain 3 times the mass of our Sun
but be 20km in diameter
What is a supernova?
•A dying giant or supergiant star can suddenly
explode causing a huge bang
•Some of the material from the star expands into
space which becomes part of nebula again
•“Recycled Star”
Black Holes
•Most massive stars
•40 times the mass of the Sun
•After the star becomes a supernova, the
gravity is so strong that the gas is pulled
inward packing it into a smaller space
•Gravity is so strong that nothing can
escape...
Black Holes
•…not even light!
Black Holes
•Astronomers cannot detect black holes
directly
•They find gas near a black hole rotating
faster & faster
How are stars classified?
•Size
•Temperature
•Brightness
Star Sizes
•All stars appear to be the same size
•Our Sun is a medium-sized star which
most stars are
•Giant Stars or Supergiants are very large
•White dwarf stars are about the size of
Earth
•Neutron stars are even smaller
Star Temperatures
•A star’s color reveals its temperature
Red/Orange
•Giants
•3,000-5,000 °C
•Betelegeuse
Yellow
•Supergiants
•6,000°C
•“Polaris”
•Sun
Blue/White
•Main Sequence/White Dwarfs
•10,000-50,000°C
•“Rigel”
What is the H-R diagram?
•Graph used to show the relationship
between temperature & brightness
Main Sequence
•Diagonal band on the H-R Diagram
•90% of all stars are main sequence
•Our Sun
What is a light-year?
•Is the distance that light travels in 1 year
or about 186 thousand miles per second
What is a constellation?
•Pattern of stars in the sky
Big Dipper
Hercules
Orion
Cancer
Pegasus