1. Supernovae
Type 1a

2. Binary Stars and Death
When two ordinary stars (about the sun’s mass) in a binary system die the results can be explosive
The more massive star will die first
Its death will not be unlike the Sun’s though the other star will affect the form of the planetary nebula.
Producing nebulae like the Rose Nebula
When the second becomes a red giant it will trigger a type 1a super nova

3. It explodes in a supernova!
Mass from the red giant “falls” onto the white dwarf…
When the mass of the white dwarf reaches the critical mass of 1.44 solar masses,
Known as the Chandrasekar’s limit
then
It explodes in a supernova!

4. Because it always happens when the mass is 1.44 solar masses,
the amount of energy created in a Type Ia Supernova is always about the same.
Thus its luminosity is always the same.
A Type Ia Supernova in another galaxy is thus a good standard candle to use to find the distance to the galaxy

5. Collision Supernova Another explanation is that…
Sometimes two white dwarfs in a binary system collide reaching or exceeding Chandrasekar’s Limit
making a Type1a supernova