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Publié le 19/03/2023

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« THE LIVE OF THE SUN The Birth: The Sun, a star constellating the Universe among many others.

Now around 5 billion years old, it is in the middle of its life.

A peaceful life that will end with his annihilation as well as all the telluric planets orbiting around him. The history of our Sun begins in the region of the Arm of Orion, 28,000 light years from the center of our galaxy, the Milky Way.

Billions of years ago, a supernova reaching the end of its life exploded generating a gigantic cloud composed mainly of hydrogen and hellum but also of dust. It holds to its equilibrium due to the thermal pressure of the molecules and dust particles that make it up.

At some point, the cloud undergoes a slight disturbance which compresses it slightly until it reaches what is called "the mass of Jeans". In 1902, British physicist James Jeans demonstrated that a gas cloud could undergo gravitational collapse.

It occurs when the gravitational attraction caused by an overdensity of a medium becomes greater than the pressure forces which tend to relax an overdensity.

When the cloud reaches the mass of Jeans, it collapses on itself by fragmenting into several parts.

Each of them collapses in turn until it reaches a minimum size that no longer allows the process to continue.

While collapsing, the temperature and pressure increases to the point of giving rise to what is called a protostar.

On an astronomical scale, the formation of the protostar is relatively rapid since it is only 50 million years old. A protostar is the phase during which the gravitational contraction of a cloud makes it possible to increase the temperature to the point of reaching the threshold for triggering the thermonuclear reaction.

During this phase, which extends over several million years, the protostar continues to absorb gases in its immediate environment.

When the core reaches a temperature of 10 million degrees, the thermonuclear reaction begins, bringing the protostar to the star stage. And the rest of the solar system in all this? The force of gravity ends up getting the better of a small part of the giant cloud which is gradually transformed.... »


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