DO NOW QUESTIONWhat life stage is our Sun currently in? What do you

think will happen to our Sun as it gets older?

The Life Cycle of Stars

Stage 1: Formation Enters first stage as a

ball of gas and dust

Gravity pulls the gas and dust together into a sphere

As the sphere becomes denser, it gets hotter and the hydrogen changes into helium

Stage 2: Main Sequence The longest stage

In the core of this type of star, hydrogen atoms fuse into helium atoms releasing a huge amount of energy

Nuclear Fusion Occurs when hydrogen changes to

helium This process releases energy that fuels

the star

2 hydrogen atoms

combine

1 helium atoms is produced

1 hydrogen

atom

1 hydrogen

atom

+

energy is

released

Stage 3: Red Giant The star expands and cools once it uses

all of its hydrogen The center of the star shrinks The star’s atmosphere then grows very large and cools The star is reddish in color Red giants size comparison to

our Sun. Note, red giants can vary in

size.

Stage 4: White Dwarf Final stage of a star’s life cycle

Has the same mass as the sun or smaller

A small hot star that is the leftover center of an older stare

There is no hydrogen left and can no longer generate energy by fusing hydrogen atoms into helium atoms About the same size

as Earth

Supernova At the end of its life,

a massive star may explode in a large, bright flash called a supernova

A gigantic explosion in which a massive star collapses and throws its outer layers into space

Chandra, Hubble, and Spitzer Space Telescope image of

Crab Nebula supernova remnant

Neutron Star Following a

supernova, the center of the collapsed star contracts to form a neutron star

A star that has collapsed under gravity to the point at which all of the stars particles are neutrons

Pulsar A spinning neutron

star that sends out radiation across space

This radiation (radio waves) is detected on Earth by radio telescopes

Vela pulsar, picture taken by Chandra X-Ray

Observatory

Black Hole An object that is so massive that light

cannot escape

If the center of a collapsed star has a mass that is more than 3 times the mass of the sun, the star may contract further because of gravity

The force of the contractions crushes the dense center of the star and leaves a black hole