What happens when a red dwarf dies

Life and death of a star

The sun is a small star and, like our planet earth, has existed for 5 billion years. Both will live another 5 billion years.

Birth of a star

Our sun, too, was just a collection of gas and dust over five billion years ago. The so-called gravitational force (or "gravity") ensured that this accumulation condensed into a gas cloud over millions of years. The denser the cloud, the hotter it is inside. The gas particles collide more and more violently. It's getting hotter and hotter. At some point it is so hot that the particles merge - a star has been created.

Small stars live much longer

A star consists mainly of hydrogen and helium particles. In its interior, two hydrogen particles merge with each other - this is called nuclear fusion. This creates a helium particle and a lot of energy. The energy in the form of heat and light is radiated into the dark, cold space. Slowly but surely the star is losing energy.

How long the “fuel” reserves last depends on the size of the star. The bigger it is, the more energy it consumes and the shorter its life. The formula for the energy consumption of a star (compared to the sun) is:

The number by how much the star is larger or smaller than our sun, to the power of 3.

So if a star is twice as big as our sun, it does not only use twice as much energy as our sun, but eight times (2 times 2 times 2). A star three times the size of the sun uses 27 times (3 times 3 times 3) more energy, etc.

A long ending

The way in which a star “dies” over millions of years also depends on its size.

Stars the size of our sun puff up towards the end and shine reddish, they become "red giants". Our sun, too, will one day meet this fate. The sun will grow so big that it will swallow the earth and all other planets in our solar system.

A red giant gets so hot that its outer shell is blown away. The shell also contains carbon and oxygen, building materials for later generations of stars and planets. When there is no more shell, the stars quickly lose energy and mass. They shrink and emit white light - they become "white dwarfs".

A white dwarf is about the size of the earth. The dwarf cools down over billions of years. For the first thousand years it is surrounded by a beautiful mist. Much, much later, the white dwarf becomes a black dwarf. This is so called because it no longer emits any heat or light. It is believed that the universe is not old enough for black dwarfs to exist.

The supernova

Stars that are many times larger than our sun have an even more spectacular finish. Instead of shrinking again after inflating, they end in a gigantic explosion, a so-called supernova. In a supernova, the outer layers of the star are thrown into space. The nucleus becomes either a faint little sun (neutron star) or a black hole.