Sirius is the brightest star in the night sky. It is very close to us, only 8.6 light years.
We only see one Sirius with the naked eye, but in fact Sirius is an binary star system , composed of a star and a white dwarf star . We call them "Sirius A" and "Sirius B" respectively. Sirius A is a star larger than the sun, with a mass of about twice that of the sun. The reason why it can become the brightest star in the night sky is, on the one hand, because it is close enough to us, and on the other hand, because it is very bright, about 23 times that of the sun. Sirius B is a white dwarf with a mass similar to that of the sun. However, the white dwarf is a celestial body with extremely high density, so it is very small in size, probably similar to the earth. Its brightness also comes from the residual temperature left after the star collapses, so the brightness is very low and cannot be seen by the naked eye.
Sirius A is more than twice the mass of sun , which means that Sirius A's lifespan is much shorter than that of the sun.
Because the larger the mass of a star, the higher the temperature and pressure inside it will be, and the more intense the hydrogen fusion will become, so the faster the fuel consumption will be and the shorter the life span. The lifespan of the sun is about 10 billion years, while Sirius' maximum lifespan is less than 2 billion years, which raises another question: When Sirius' lifespan reaches its end, will it bring danger to the earth? An extremely intense celestial activity breaks out at the end of life of a massive star, which is called " supernova explosion ". What is a supernova explosion? Simply put, as a star is exhausted, the nuclear fusion gradually goes out, and the outward radiation expansion pressure disappears, so the star will collapse sharply toward the center under its own gravity.
The star matter collapses sharply toward the center, and then it will rebound violently, releasing extremely huge energy in an instant. This is the explosion of a supernova.
The power of supernova explosion is very strong and the scope of it is affected is very wide. It is generally believed that the area 50 light-years near the stars where supernova explosions will be affected. If there is a habitable planet within this range, its ecology is likely to be destroyed. The distance between Earth and Sirius is only 8.6 light-years. If a supernova erupts in Sirius, the Earth will obviously be in danger, but don't worry, because Sirius will not have a supernova eruption. Why? Because its mass is insufficient, only stars with a mass of 8 times the mass of the sun will usher in a brilliant supernova explosion at the end of their lives.
Sirius A will not have a supernova explosion, but it does not mean that Sirius will not have a threat to the earth, because there is also a Sirius B in this system.
Sirius B is a white dwarf with strong gravity and will absorb surrounding matter, thereby increasing its own mass. Indian-American astrophysicist Chandrasekha believes that the mass of a white dwarf is limiting. If the mass of a white dwarf exceeds 1.44 times the mass of the sun, then it will explode in the La supernova, thus becoming an neutron star . The explosion of a La type supernova is also a violent celestial activity. In an instant, energy will be released in the form of high-speed shock waves, and all planetary ecology within the affected range will be destroyed by it.
Will a La-type supernova explosion occur in Sirius B?
The only material that can be absorbed near Sirius B is Sirius A. However, the distance between the two stars is very far, reaching about 3 billion kilometers. At such a distance, Sirius B cannot absorb the material of Sirius A, but Sirius A is not static. It is a star, and a relatively short-lived star. It will expand at the end of its evolutionary stage and become a red giant. The radius will increase by hundreds of times. Then as the radiation expansion pressure disappears, it will collapse into a white dwarf.Even if Sirius A expands into a red giant, it is still far enough from Sirius B, so there is no need to worry about being absorbed. But the problem is that after Sirius A collapses into a white dwarf, a large amount of stellar matter from the previous one will be thrown into space, and some of these matter will become the nutrient for Sirius B.
But we don't need to worry too much.
First of all, in theory, Sirius B has the possibility of exceeding the limit of Chandrasekha , but this possibility is not great. Although it will absorb some of the matter thrown out by Sirius A, it is very difficult to achieve 1.44 times the mass of the sun. Secondly, although Sirius A is a relatively short-lived star, it is only for the star itself. For us humans, its lifespan is actually very long. You should know that our ancestors completed the evolution from , the Australopithecus to modern humans in just 3 million years. The lifespan of Sirius A is as long as one billion years. What will the earth look like in more than one billion years and how much human civilization will develop? We cannot imagine at all.
