1. Part 3 Fate of the most massive stars
Stellar Evolution
Part 3
Fate of the most massive stars

2. A Star with a mass of at least 1
A Star with a mass of at least 1.5 times that of the Sun generates much higher Temperature and Pressure in its core. After less than a billion years… it starts to run out of hydrogen in its core and fusion slows: Its core shrinks and gets hot enough to… Fuse Hydrogen into Helium in a shell outside the core AND Begin to fuse Helium into Carbon in its core The star itself expands The outer layers cool and it becomes a red supergiant

3. When it runs out of helium in its core It shrinks And heats up Carbon begins to fuse into Neon in the core While He→Carbon, and H→He in shells. Each time it runs out of fuel in the core a new reaction begins there and the former reaction starts in a shell. It gradually heats up becoming a Blue Supergiant Eventually in the Core Silicon→Iron and outside the core O→Silicon, Neon→O, Carbon→Neon, He→Carbon, and H→He fuse in shells

4. Supernova!
Eventually the Star starts to run out of silicon in the core Fusion slows and the star becomes a red supergiant again Since Iron doesn’t release energy when it fuses, It needs vast amounts of energy to fuse, so Fusion in the core stops. The core shrinks rapidly in microseconds. The Outer-layers crash inward superheating the core to billions of degrees. Iron and other elements fuse into heavy metals and The Outer-layer bounces back the Star Explodes… A Supernova! (Type 2)

5. Nebulae
The Nebula created by a supernova expands at 10,000 km per second!
And is chaotic in appearance

6. Neutron Stars
The core of a star with between 1.5 and 3 solar masses will collapse after the Supernova
It becomes so dense that Electrons meet protons and charges cancel…
A Neutron Star
With a thin crust of Iron.
It begins to spin super-fast with a period is as little as a second!
This generates a strong magnetic field and a beacon of radio energy that acts like a spinning search-light.
That appear to us as a Pulsar, a source of a rhythmic radio signal first thought to be intelligent aliens!

7. Black Holes
If the core of the star is 3x the sun’s mass or more has enough mass so that when it collapses the gravitational field becomes so strong that the escape velocity near it becomes faster than light.
Light itself cannot escape…. A Black Hole.

8. The distance from the black hole called the Event Horizon is where escape velocity is equal to light-speed.
Any closer and nothing can escape!
Black holes are detected by the jets, fluctuating magnetic fields, infrared and X-ray light produced by the whirlpool (Accretion disk) material falling into the “hole”.

9. This is an image of a Black Hole at the core of the Galaxy
Centaurus A!