What happen when our Sun dies and could it become a black hole: scientists' answer

Our Sun will have reached the final stages of its existence in about 5 billion years, having used up all the nuclear fuel in its core. Unless a medical miracle happens soon, there is 0% chance that anyone alive today will be able to see this happen. But, of course, both ordinary people and scientists are wondering what the demise of our luminary will look like and will turn into a voracious black hole.

The professor of physics and an expert on black holes at the University of Sussex in the UK Xavier Calmet shared what will happen in the distant future of our solar system in the commentary to LiveScience. He is convinced that a black hole will never form near Earth, but our home may not survive the demise of the Sun as it is.

The Sun's death will begin in 5 billion years when it has burned up all its fuel and can no longer resist its gravity. As a consequence, the outer layers of our luminary will fly apart and quite possibly destroy the Earth or all life on it. At the same time, the Sun's core will shrink to an incredibly dense state.

Thus, our dying Sun will enter the red giant phase and it won't even be the last phase of its death.

As Calmet explained, when the Sun becomes a red giant about a billion years after its core runs out of hydrogen, it will expand to the orbit of Mars, engulfing the inner planets, possibly including Earth.

Next, the outer layers of the red giant will cool and atomize, forming a planetary nebula around the Sun's smoldering core. This will be the final stage in the death of our star, which will eventually turn into a white dwarf, whose size will be about the same as the size of the Earth. Right now, the Sun is 109 times the diameter of our planet.

So, as is already obvious, our Sun will never turn into a black hole. Here's a simple enough argument for that: no matter how gigantic the Sun is from our perspective, it's still too small to turn into a black hole.

"It's very simple: the Sun is not heavy enough to become a black hole," Calmet explained.

He noted that several conditions, including its composition, rotation and the processes that govern its evolution affect whether a star can become a black hole. But the right mass is the main condition.

"Stars with an initial mass of about 20 to 25 times the mass of our Sun have the potential to experience the gravitational collapse necessary for black holes to form," Calmet noted.

This threshold, known as the Tolman-Oppenheimer-Volkoff boundary, was first calculated by Robert Oppenheimer and his colleagues.

Scientists now believe that a dying star must leave behind a core about two to three times the mass of the Sun to create a black hole. The Sun's core, as mentioned above, would shrink to the size of the Earth.

At the same time, stars that are capable of becoming black holes go through almost the same phases of death.

When a star exhausts the fuel in its core, nuclear fusion of hydrogen into helium still occurs in its outer layers. When the core collapses, the outer layers expand and it enters the red giant phase.

Meanwhile, massive stars that can create black holes go through several such periods of collapse and expansion, losing more mass each time.

As the physicist explained, this happens when stars fuse heavier elements at high pressures and temperatures. The process continues until the core of the star is entirely made up of iron, the heaviest element a star can create. Such a collapsed star then explodes in a supernova, scattering even more of its mass into space.

It subsequently turns into a black hole and begins to feed on nearby gas and dust.

However, our Sun will never reach the stage of melting iron and will not turn into a black hole.

Earlier OBOZREVATEL shared what will happen when the Milky Way crashes into Andromeda.

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