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