Not All Stars are the Same• We will examine the following stages of life

for stars: ▫ Birth▫ Early life▫ Major part of life▫ Old age▫ Death▫ Remains

• The results of each stage will be different for each star depending on its mass

A Star is Born!A star is born from

a cloud of dust and gas called a nebula

Nebula means “mist” in Latin

Early LifeA small star (like our Sun) will gradually turn

into a hot, dense clump that begins to produce energy.

This happens when parts of nebulae collapse in on themselves

Gravity and mass will increase causing a tightly packed sphere of matter to form

Eventually the pressure gets so high that nuclear fusion occurs

The Major Part of LifeThe star really turns

“on” when nuclear fusion starts transforming Hydrogen into Helium

This produces energy (light & heat)

The Star stays in this state for most of its life

The length of a star’s life depends on its mass and how quickly it uses up its Hydrogen

For a star similar to our Sun, it will use nuclear fusion to produce energy for about 10 billion years

Old AgeAfter a while, all of the

hydrogen in the core of the star gets used up

Helium is then used for nuclear fusion

The core starts to collapse and the outer layers of the star expand

Red GiantAs the outer layers

expand, the star becomes a large, cool red giant

Consider the size difference between the Sun and a Red Giant

DeathOuter layers of the Red

Giant drift awayThe core shrinks The star becomes a

small, hot, dense white dwarf star

Sirius (Dog Star)

Sirius B – White Dwarf

The white dwarf star will eventually cool off, and fade away

Remains

Life of Bigger StarsFor stars 10 times the

size of the Sun:In a short time will

become a hot dense clump, and use nuclear fusion to produce energy

Uses nuclear fusion for a few million years

They are 5000 times brighter than the Sun

For stars 30 times the size of the Sun:In a very short time

will become a hot dense clump, and use nuclear fusion to produce large amounts of energy

Uses nuclear fusion for only about one million years

They are extremely bright

Old AgeLarger stars swell to

become Red Supergiants

Red Supergiant

Death of Bigger Stars

Bigger stars have a more extravagant death

Their cores collapse inwards, sending the outer layers exploding into a supernova

Remains of Bigger StarsStars that are

around 10 times the size of the Sun will turn into a neutron star after the supernova.

Gases from a neutron star drift off as nebula and get recycled

Black HolesThe largest of stars will end up as black holes

http://hubblesite.org/explore_astronomy/black_holes/index.html

Eagle Nebula

Heart Nebula