Stars!!!!

Galaxies and the Universe too!

Stars are far away!• The closest star to Earth is the

sun.• The next closest is Proxima

Centauri• If you can travel at the speed of

light it would take about 8 minutes to get to the sun and 4.2 years to get to Proxima Centauri.

What is a Light Year?

• The distance light travels in one year. 9.5 trillion KM (This is a unit of distance, not time)

• Light speed is 300,000 km/s

What is a Solar System?

• A star and the planets that revolve around it

What is a Galaxy?

• A cluster of stars• There are four different types

Elliptical Galaxy

Spiral Galaxy

Irregular Galaxy

Lenticular

What is the Universe?• Space and

everything in it.

• Made up of billions of Galaxies.

• The galaxies are far apart so most of the universe is empty space.

What is Parallax?

• The apparent change in position of an object when you look at it from different places.

• Astronomers use parallax to measure distances of nearby stars. They measure how much the star moves in the sky over a six month period

Classifying Stars!

• Astronomers classify stars by their size, temperature, and brightness.

• Size= Small, medium, and giant• Color and Temperature=

–Red= about 3,200 degrees Celsius–Yellow= about 5,500 degrees Celsius–Blue= over 10,000 degrees Celsius

Brightness• Apparent

Magnitude- A stars brightness as seen from Earth

• Absolute Magnitude- A stars brightness if it was a standard distance from Earth

Hertzsprung- Russell Diagram

• Diagram that classifies stars by their brightness and temperature

• Most stars are Main Sequence Stars. This is a diagonal band on the diagram that shows surface temperature increasing as brightness increases

Hertzsprung- Russell Diagram

The Birth of a Star

• Stars start out a Nebula( large amount of gas and dust). Gravity then pulls the Nebula together creating a protostar. A star is actually born when the gases contract so much Nuclear fusion starts

Formation of the Solar System

Life of Stars

• A stars life depends on its mass

• Small stars live for about 200 billion years

• Medium stars live for about 10 billion years

• Large stars live for about 10 million years

Star DeathsWhen a Star Runs Out of Fuel

• White Dwarfs

• Neutron Stars

• Black Holes

White Dwarfs

– Created from small and medium stars– When they run out of fuel the expand to a red

giant– These gases eventually blow away leaving

the blue white core– They are about the size of Earth but with the

mass of the sun– When it dies it is called a black dwarf

Neutron Stars

• Super Nova is when a giant or super giant star explodes

• What is left over is called a neutron star – Smaller and denser than white dwarfs– They can have the same mass as the sun but

can be the size of an asteroid

Black Holes

• This only happens to the most massive stars.

• They become supernovas with more then 5 times the mass of the sun left.

• The gravity is so strong that it pulls all the gases in so close that not even light can escape

Quasars

• Quasi- stellar objects

• They are the most luminous, powerful, and energetic objects known of at this time. They seem to inhabit the centers of active young galaxies and can emit up to a thousand times the energy output of our entire galaxy

Star Systems

• More then half of all stars are members of groups of two or more stars, called star systems

• Binary Stars- two stars• Eclipsing Binary- a

star system in which one star blocks the light from another

History of the Universe

• Big Bang Theory: The universe formed in an enormous explosion about 10-15 billion years ago.

• All of the galaxies are moving away from a central point (Edwin Hubble discovered this)