In our last article we read about the Red Giant stars. Only those stars end up as Red Giants that:
- Are at least 1/3rd the mass of our own Sun or,
- Have same mass as our Sun or,
- Are up to 8 times as big as our Sun.
With these figures in mind, 97% of all stars that are present in our Milky Way galaxy will end up as Red Giants and that includes even our Sun! The question is, ‘what happens after the Red Giant state?’ We covered this partially in our article on Red Giant stars but now, let us learn that in details. Just a heads up, after the Red Giant state comes the White Dwarf stage. So, let us visit the skies once again and learn 20 interesting White Dwarf star facts. You ready?
Interesting White Dwarf Star Facts: 1-10
1. After a Red Giant gets rid of outer layers as planetary nebula, what remains is the central core that is rich in carbon and oxygen.
2. Because the size of the remnant core is not big enough, the core fails to produce temperature required for fusing carbon atoms. The required temperature is extremely high at 1 billion Kelvin.
3. Though the temperature fails to reach that high, the core is still hot at around 100,000 Kelvin and just hangs out there in the vast universe and goes through gradual cooling.
4. While the core sits there and cools gradually, it keeps emitting faint white light along with low-energy, soft X-rays. This explains the name White Dwarf.
5. The cooling process takes place over next hundreds of billions of years (it is better we call this time frame eternity). After all the heat trapped in the remnant core is released in space, the core stops emitting light and becomes absolutely dark. This is when it is known as black dwarf.
6. Though we call it a White Dwarf, it is far beyond being a dwarf that we are usually accustomed to think of. A White Dwarf star is as big as Earth in terms of size.
7. In terms of mass, a White Dwarf has the same mass as our Sun. So, the total mass of Sun compressed and put in an object the size of Earth. This makes White Dwarfs extremely dense objects.
8. A White Dwarf can have more mass than that of our Sun but the maximum it can attain is 1.4 Solar Masses (that is 1.4 times the mass of our Sun). This is called Chandrasekhar Limit. Well, we are not going to go into those technical explanations. Just know that the mechanism that prevents White Dwarfs from collapsing on themselves because of their own gravity cannot support a mass bigger than 1.4 Solar Mass (M☉). This mechanism is called electron degeneracy pressure.
9. Again, it is not necessary that a White Dwarf will have at least the same mass as our Sun. It can have lower mass. The lowest possible mass is 0.17 M☉. Most of the White Dwarfs have mass within the range of 0.5 M☉ and 0.7 M☉.
10. Just to put in perspective, if we manage to scoop out a teaspoonful of matter from a White Dwarf, it will weigh as much as 5.5 tons – almost equivalent to the weight of an elephant! Got it?