Please enable JavaScript.
Coggle requires JavaScript to display documents.
The Evolution of the Stars - Coggle Diagram
The Evolution of the Stars
Hertzsprung-Russell Diagram
If you plot temperature along luminosity, you can see whee the most stars are.
The Sun's Evolution
Step 1
Start off with a big cloud of gas - cool and low in temperature
Gravity brings this gas together, and eventually this gas forms a star
Step 2
The has cloud collapses and a star forms. The star is a star when nuclear fusion occurs
Step 3
The Main Sequence: Nuclear fusion warms up the star from the energy released. Hydrogen fuses into helium, and helium accumulates in the core.
Step 4
The Giant Branch. The core runs out of hydrogen and becomes a giant star.
The layer around the core, hydrogen still sticks to make helium and energy, causing this layer to expand. Nothing happens in the core
Red Giant Phase
Fusion continues in the middle layers, and these heat and expand - it appears brighter and cooler
Core helium flash
Hydrogen fusion around the core, heats the core until it is hot enough for helium to fuse into carbon. Inner layers expand and so nuclear reactions slow, and outer layers shrink and fade
Asymptotic Giant Branch
Now the star has a carbon core, surrounfed by shells of fusing helium and hydrogen. These shells expand due to heat and the star grows larger and redder.
Step 9
Outer layer are blown away as planetary nebula
Step 10
The core is left behind as a white dwarf star
The Evolution of a Massive Star
Step 1
A massive gas cloud, collapses and gravity brings it all together
Step 2
Because gas cloud is big, it forms a very big star
Step 3
Lives in the main sequence for less than 100 million years (lives fast and dies young)
Massive sequence stars become supergiant stars. The temperature of the core is very hot allowing helium to fuse into carbon - no helium flash
Step 4
Instability strip. Some of these massive stars are unstable, and they pulsate. The energy inside the star heats the gas and the star expands, and as expands it cools so gravity pulls it back together. This is a pulsating variable star
Nucleosynthesis: when a high mass star runs out of helium in its core, the core shrinks and heats. Creates more than carbon - neon, oxygen and silicon.
Step 5
Now a supergiant, so huge amounts of mass ejected into stellar winds. Nuclear fusion stops at iron
Supernova explosions
If the core is not being heated, it will collapse, and gravity wins causing a massive explosion = end of life
Step 7
Outer layers all removed and core left behind as a neutron star or black hole.
Gravity depends on how much mass there is, everything with mass has gravity.
Einsteins general theory of relativity
This unifies space and time into a single entity = space-time
Gravity is the curvature of space-time, and the curvature is caused by the presence of matter
Light has no mass, so this proved gravity is curved space rather than a force
Cataclysmic Variables: Binary star systems where gas is flowing between 2 stars. Accretion disks