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 Elliptical Irregular

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

Stop HERE!

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 9.5 million million km

What is a constellation? Pattern of stars in the sky

Big Dipper

Hercules

Orion

Cancer

Pegasus