this is what science tells us about the future of our star

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The development that astrophysics has experienced during the last century has been spectacular. The human being has always felt an enormous fascination for the objects that he could observe in the sky, so much so that we know for sure that Socrates and Plato reflected on them and their nature. nearly two and a half millennia ago with the same curiosity and restlessness that have since fed the many scientists who have brought us to where we are today.

We still have a long way to go to unravel the mysteries of the cosmos, there is no doubt about that, but one of the areas in which astrophysics has advanced the most in recent decades is stellar evolution. This does not mean at all that we know in detail what the life of all stars is like, but the tools that physics and mathematics have placed in our hands allow us to know quite well the stages through which the life of a star passes. And ours, the one that bathes our precious planet with its energy, is no exception.

It all starts with a cloud of gas and dust

Gravity is an inexhaustible force. She is the true engine of the universe, and the one responsible for the birth of the stars. Its origin takes place from the clouds of gas and dust scattered throughout the cosmos, so that when its density is high enough, gravity triggers a mechanism known as gravitational contractionwhich little by little condenses the matter of the cloud to give rise to a protostar or stellar baby.

The life of all stars is profoundly conditioned by their initial composition, and, above all, by their mass.

The life of all stars is profoundly conditioned by their initial composition, and, above all, for its mass. They are about 70% hydrogen, 24-26% helium, and 4-6% chemical elements heavier than helium. The most massive stars, those that manage to condense more matter thanks to gravitational contraction, consume their fuel much faster than less massive stars. They are the perfect candidates to end their days in the form of a neutron star or a black hole.

For the ignition of hydrogen in the core of the protostar to begin thanks to nuclear fusion reactions, its innermost region must reach a temperature of ten million degrees Celsius. Once again, what is responsible for these conditions is gravity, which relentlessly compacts the matter and causes it to gradually heat up until, finally, the nuclear furnace is turned on. This is the moment in which the birth of the star occurs, beginning a phase of its life known as main sequence.

Cosmos

Stars are born from the clouds of gas and dust scattered throughout the cosmos and under the tireless action of gravity.

During this stage the star obtains its energy from the fusion of hydrogen nuclei, and begins the production of helium, which will be followed by other chemical elements in later stages. The composition of the star begins to change at the same instant that the nuclear furnace is turned on, but what is most surprising is the mechanism that allows the star to stay stable From this moment.

Gravity continues to compress and heat the star’s matter, but the combustion of its chemical elements generates radiation and gas pressure to keep it at bay. Gravity pulls the star’s matter inward, toward its core, and radiation and gas pressure pulls the star’s matter in the opposite direction, outward. These opposing forces keep the star in hydrostatic balancealthough it is constantly readjusted as it consumes its fuel and its composition changes.

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If the star is massive enough, it will continue to consume its helium reserves, producing carbon and other chemical elements, which will also be gradually consumed through nuclear fusion reactions. But this process has an expiration date. From iron it is not possible to obtain energy through nuclear fusion processes, so that when the core of the star evolves through the stellar nucleosynthesis until it is made up of iron, energy production stops.

At that moment, the pressure of radiation and gases is not able to compensate for the pull of gravitational contraction, so the star collapses. Gravity and pressure from the upper layers suddenly compress its core, so that all the material above it falls onto it with enormous energy and bounces back out into the stellar medium. There has just been a supernova, a phenomenon that has caused much of the matter that the star has synthesized to be scattered throughout the cosmos. Those chemical elements will shape new clouds of gas and dust from which new planets and stars may be born.

Nebula

This image, taken by the Hubble Space Telescope, shows us a portion of the Lagoon Nebula, located in the constellation of Sagittarius.

What remains of the massive star after the supernova, the remnant, is another colossal object. Possibly that terrifyingly energetic explosion will leave behind a neutron star, but if the mass of that object is high enough there is a possibility that it will give rise to a quark star. Or even a black hole.

The superficial review that we have just done can be useful not only to intuit what the life of a massive star is like; It can also help us understand how the life of our Sun has been until reaching the stage in which it is currently. And also to predict how is your future going to be. However, if you want to know in more detail the stellar evolution I suggest you take a look at the article in which we address it in more depth. In the same way, if you are curious to know more about neutron stars and quarks, you can consult the article that I link right here.

Our Sun has only consumed 40% of its fuel

The estimates of the scientists defend that the star that bathes us with its energy has approximately 4.6 billion years. They also believe that it formed at the same time as the planets orbiting it, so this is also the approximate age of the solar system we live in. For us the Sun is very special because without its energy life on our planet would not be possible, but in reality it is a relatively small star. There are millions of stars like her scattered throughout the cosmos.

Astrophysicists estimate that the Sun has consumed about 40% of its fuel

It is currently in the main sequence phase, so, as we have seen a few paragraphs above, it is consuming hydrogen in its nucleus and producing helium. Its luminosity is gradually increasing due to the fact that this last chemical element is accumulating inside it, and also because the processes of nuclear fusion are gradually spreading towards the outermost layers.

Astrophysicists estimate that the Sun has consumed about 40% of your fuel, so it will remain within the main sequence for many millions more years. But this is not the only thing they know. The most advanced models of stellar evolution reflect that it will reach its maximum effective temperature within the main sequence phase in approximately 3 billion years.

massivestar1

Our star has a life of about 7 billion years ahead of it, although it will not always have the appearance and size it has now.

And within 5 billion years according to some estimates, or 6.4 billion according to other studies, its core will no longer contain the hydrogen necessary for thermonuclear processes to continue. At that moment it will turn off, and will transform into an inert core in which helium will predominate. Nuclear fusion will continue to take place around the core, the star’s volume will increase significantly, and its luminosity will be twice what it is today.

Fortunately, there is still a lot of time for the thermonuclear processes in the core of the Sun to stop, but that will not be the moment that could end life on our planet. And it is that astrophysicists believe that it will be enough for the luminosity to increase until it is 1.1 times the current to trigger a greenhouse effect on Earth that is incompatible with life.

The future of the universe: what science tells us about the (far) end the cosmos is heading towards

The luminosity of our star will continue to increase, and when it is 1.4 times current the oceans will evaporate, although we will not be here to see it. In any case, we can be calm because the most advanced models estimate that the biosphere will not be threatened by the Sun for about 3.5 billion years. Those same models predict that our star has a life of about 7 billion years ahead of it, although it will not always have the appearance and size that it has now.

As I mentioned a few lines above, as the thermonuclear processes stop in the solar core, the volume of the star will increase significantly until it becomes a red giant. In this phase the star will lose a lot of mass, and, although astrophysicists are not entirely sure about what its life will be like from here, they believe that its size will increase enough to end up devouring the planet Mercury.

neutron star

A one-cubic-centimeter fragment of a neutron star weighs roughly 1 billion tons.

At this time the Sun will emit approximately 2300 times the current radiation. It will continue to consume hydrogen in the layers surrounding the inert helium core, and later the fusion of helium nuclei at its heart will begin. Its luminosity at that time will be 40 times higher than it is now, and it will continue to expand until it is 150 times larger than it is now.

The biosphere will not be threatened by the Sun for about 3.5 billion years.

The models with which astrophysicists work do not allow us to know precisely if the expansion of the star will cause it to also engulf Venus and the Earth because its loss of mass will be very significant. In any case, at that time solar radiation It will have completely destroyed the Earth’s atmosphere.

Its point luminosity will continue to increase until it is 5000 times the currentand at the end of its days the gravitational collapse will expel its outer layers from the stellar medium, leaving as a remnant a white dwarf with a size very similar to that of the Earth and a mass that will be approximately half of that of the Sun today. .

Everything we have just seen invites us to accept that stars are living objects, and as such, they are born, grow, die and reproduce. In this order. With a lot of effort, and also with a bit of luck, the human being may be able to establish himself beyond our planet, and when conditions on Earth are incompatible with life, we may have spread to other regions of the cosmos. Or maybe not. In any case, if we stick to the expiration date imposed by our star, we have 3.5 billion years to find a solution.

Images: NASA Goddard Space Flight Center

The development that astrophysics has experienced during the last century has been spectacular. The human being has always felt an…

The development that astrophysics has experienced during the last century has been spectacular. The human being has always felt an…

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