4.5 billion years ago, a medium-sized star formed in the middle of a huge cloud of gases and dust. Around it, matter was collapsing and giving shape to the stellar bodies that today orbit this, our Sun, president of our home, and among which is, of a pale blue, our planet.
But one day the star that gave us life will run out of fuel. It is currently generating helium from the constant fusion of hydrogen atoms in its nucleus. When it stops doing it, it will die and with it, the rest of the celestial bodies, including the Earth.
Once the Sun definitively depletes its hydrogen reserves, it will begin to fuse helium atoms and in this process it will expand until it reaches the orbit of the Earth as a red giant. Scientists do not know for sure if at that moment, in another 4,500 million years, the unstoppable growth of its outer layers will also engulf the Earth (in its expansion it will do the same with Mercury and Venus), but what it will not There is no doubt that our planet will have been incompatible with life long before.
Scientists agreed that the star will die, and when. What they weren’t sure of is how, until now. Thanks to new research, scientists know more details about what the final end of the Sun will be like and, inevitably, that of our home.
The study has been prepared by an international team of scientists, who have been able to predict that the Sun will turn into a massive ring of luminous gas and dust , known as a planetary nebula.
But the study has not only determined what the end of the Sun would be like, but, finding out, has resolved a conflict that has lasted more than 25 years in the scientific community: the hypothetical end that is now predicted to the Sun, theoretically, was not possible according to ancient models, because it was believed that the Sun, as a medium star, was not capable of leaving this nebula behind. Instead, the new research reveals that not only the most massive stars can give rise to planetary nebulae; The low-medium mass ace, like our Sun, can also, although of less intensity.
A spectacular ending
When a star dies, it has two possible endings. The first, and most spectacular, is the explosion of its outer layers in a massive explosion, in the form of a supernova. The second, somewhat more discreet, is the conversion into a white dwarf. That is, it will either slowly turn off until it is cold and unusual; or it will explode, leaving behind a cloud of stellar dust that could later give rise to new stars and celestial bodies.
This spectacular ending is the same one reached by 90% of the active living stars that we can observe today in our universe. But, for years, scientists weren’t sure whether the Sun would follow the same path as many of its peers. As we say, it was believed that its mass was not high enough to generate a planetary nebula.
Now, new models show that after the star’s death, its outer layers heat up three times faster than previous research showed. This would make it much easier for a low-mass star, like the Sun, to form a bright planetary nebula.
Therefore, although the Sun would be the lowest mass star that could produce a visible planetary nebula, it could do so, and indeed it will do so when it dies, the researchers say.
To determine what a star will become in the twilight of its life, the team used a model capable of predicting the life cycle of stars. The model was used in turn to determine the brightness or luminosity of stars of different sizes and ages.
The research is published in the journal Nature Astronomy . An exciting discovery, since it allows, not only to venture the end of our Sun, but also supposes a way to measure the presence of stars of billions of years in distant galaxies.
Source: The mysterious age invariance of the planetary nebula luminosity function bright cut-off , Nature Astronomy (2018). nature.com/articles/doi:10.1038/s41550-018-0453-9
