Planets in our galaxy.
For most people, the phrase “a star like the Sun” is equivalent to a picture of a friendly, warm, yellow star accompanied by a retinue of planets where life may be maturing. However, new research by astronomers Volker Bromm and Abraham Loeb of the Harvard-Smithsonian Center for Astrophysics (Cambridge), which was announced at the 203rd conference of the American Astronomical Society in Atlanta, showed that the first solar-type stars were just lone plasma balls moving through a Universe devoid of planets and even more so of life (at least, the first solar-type stars). the only kind of organic life that we know so far).
These stars were born, evolved, and died in a barren, lifeless isolation, but over time they helped change the universe, they are responsible for the synthesis of heavy elements like carbon and oxygen, which eventually led to the appearance of the first planets like our Earth.
“The window for life opened somewhere between 500 million and 2 billion years after the Big Bang,” Loeb says. This loneliness is a natural stage in the history of our universe.”
And the very first generation of stars did not resemble our Sun at all. They were white-hot, massive (two hundred times as massive as the Sun) , and very short-lived. Burning for only a few million years, they exploded into supernovae at the end of their lives. However, those very first stars began an important process in the universe, scattering vital elements like carbon and oxygen, which served as the building blocks for the planets.
“We used to model the explosions of the first supernovae to track their development and estimate the amount of heavy elements (elements heavier than hydrogen and helium) that they could produce,” says Bromm. “We have now concluded that a single first-generation supernova is capable of producing enough heavy elements to form the first sun-like stars.”
Bromm and Loeb showed that many second-generation stars had sizes, masses, and therefore temperatures similar to our Sun. These properties are a consequence of the influence of carbon and oxygen at the time of star formation. Even a ten-thousandth part of the amount of these elements found on the Sun was enough to allow the birth of small stars like our Sun.
However, the low prevalence of key elements prevented the formation of Earth-like planets near those first sun-like stars. It was only when the next generations of stars evolved, died, and enriched the interstellar medium with heavy elements that the birth of planets and life on them became possible.
“We know that it takes a lot of supernova explosions to create all the heavy elements that we find here on Earth, in our Sun, and in our own bodies,” Loeb says.
Recent observation confirms this conclusion. When studying the discovered exoplanets, a clear correlation was found between the presence of planets in the star and the prevalence of heavy elements (“metals”) in this star. That is, a star with a higher content of” metals ” – heavy elements – is more likely to have a planetary system. On the contrary, the lower the content of “metals” in a star, the less likely it will have planets.
“We are now just beginning to study the question of what minimum heavy elements are necessary for the formation of a planet, so it is difficult to say exactly when the window opens for life. But it is clear that we were very lucky that the content of “metals” in our Solar System was high enough for the Earth to form,” says Bromm.
The universe is approximately 13.7 billion years old. NASA’s WMAP satellite, studying the microwave background, allowed us to determine the time of the appearance of the first generation of stars: it happened about 200 million years after the Big Bang. And last July, American astronomers found a planet that probably originated 12.7 billion years ago – it is much older than the theory allows. So the question of when the stars stopped being lonely, still remains open.