What is the main phase of life

The evolution of sun-like stars

It is a happy coincidence that the sun does not have fifty percent more mass for the emergence of highly developed life. Then she would already be a red giant and life would not be possible on earth. Of course, this is all the more true for stars with five or more solar masses.

How old is the sun And how old is the earth? Both were formed about 4.5 billion years ago. And how long will both continue to exist? That should be about the same time again, so the sun has half of its life behind it. For the sun and comparable stars, the development is relatively slow. The most massive stars, which only exist for about a million years, are completely different. Perhaps, or precisely because of the long time, life could come into being on earth.

When the solar system was formed in a protostellar disk, all the matter required for life was present. This originated largely in the precursors of today's massive stars, which produce the heavier elements (carbon, magnesium, iron, and so on) in large quantities. The massive stars return them to interstellar space in their final explosion, the supernova. There this matter turns into dust, which promotes star formation in dense gas clouds. And so the heavy elements are incorporated into new suns and planets. The sun also contributes to the production of carbon and oxygen, and thus to possible life on later planets.

The Spirograph Nebula IC 418

The sun is slow, but it is still changing! Since it was formed, its brightness has even doubled - which has also had an impact on the planets. Thanks to the thermostat effect of the earth's atmosphere, it is still pleasant here, despite major climatic fluctuations over the long period of a thousand million years. Nevertheless, in 4.5 billion years, the long-term balance will reach extremes. The sun then enters the last phases of life and it will go up and down!

In the first phase of the “final spurt” of sun-like stars, they quickly become brighter - a thousand times brighter in about a hundred million years. They become more reddish and puff up - they become “red giants”. The extent of the sun will extend beyond the earth's orbit. With such an expansion as a red giant, the sun can barely hold onto its outer shells - they are blown away. Then inside, which has become much hotter than it ever was, the helium burns and carbon and oxygen are produced. The sun calms down and shrinks to a normal level.

In the second phase, the sun lights up again to become a giant again. She blows off her outer layers again. But this time these contain some of the carbon and oxygen produced inside. Building material for later generations of stars and planets is released into interstellar space.

In the third phase, the sun finally shrinks and becomes very hot on the surface as well. The gases that were previously blown away light up due to the high-temperature radiation. Now everything that the stellar wind has blown away becomes visible in the form of a planetary nebula. Such luminous nebulae are called "planetary nebulae" for historical reasons, although they have nothing to do with planets - but in early telescopes they looked very similar to the planets, hence the name. The rest of the sun will slowly burn out without its own source of energy. In doing so, it becomes a “white dwarf”, which in turn becomes a cold ball of hydrogen, helium, carbon and oxygen much later.