Our Sun is just one of the countless ordinary stars present in the universe, but it holds great value for us and the Earth. The Sun’s gravitational force keeps the planets in orbit. We gain energy from the Sun both directly and indirectly–the Sun’s energy fuels all life on Earth. However, our Sun is not immortal, and like all other stars, it runs on hydrogen fuel. What will happen if the Sun finally runs out of fuel and dies? In this article, I’ll briefly explore the formations, properties, and death of various types of Stars. Here’s how and when Our Sun will die out.
The Sun and Stars
Stars are generally formed by the contraction of an interstellar cloud of gas known as nebulae consisting of majority hydrogen and helium and a few heavier elements. A star forms in the center of the clouds, whereas the outer parts cooled down, causing the concrete heavy elements and ice in that region to collide and eventually result in rocky planets. Once the star reaches the main sequence, it converts hydrogen to helium and releases energy; it produces light as a by-product.
The Sun, a typical star, produces light as a by-product from its primary function of converting hydrogen to helium via nuclear fusion. Photons are created in this nuclear reaction in the Sun’s core and make their way outside. They start as gamma rays but gradually lose their energy as they diffuse outside and reach the Earth in visible radiation. In short, the source of light of our Sun and all other stars is energy produced from nuclear fusion.
Stars are chemical factories whose main function is to covert lighter elements to heavier ones. Only hydrogen and helium were formed in the Big Bang nucleosynthesis. The rest of the elements on the periodic table are produced by the stars. These nuclear fusion reactions take place inside the cores of the stars. The most massive stars produce heavier elements. Most main sequence low-mass stars can go beyond helium and produce carbon. Iron is the dead end for nuclear fusion, even for more massive stars, as they require external energy to go beyond. In supernovae explosions, the titanic blasts can sometimes create enough energy to forge the heaviest elements, even uranium.
Death of Stars
The masses of stars determine most of their characteristics, including how they’ll die out. The more massive a star is, the faster it will run out of fuel. Less massive stars have the longest lives. Our Sun is in the middle range of both the mass and life spectrum. Once they run out of hydrogen fuel, stars, roughly the size of our Sun, will go through an expanding Red Giant phase, then end up as a white dwarf emitting materials to outer space as a colorful Planetary Nebula. Billions of years from now on, the death of our Sun will be visible from millions of light-years away as one of the most beautiful and colorful objects in space.
White Dwarf stars
A white dwarf star is the end state of most stars in the universe–these are average-sized stars such as our Sun. Stars are usually kept stable by balancing the thermal radiation pressure or gas pressure and its force of gravity. As the star gradually consumes its fuel, it cools down, and the thermal pressure drops, leading the star to shrink and become smaller and smaller. Once this happens, the electrons inside the star become compressed and emerge the electron degeneracy pressure. The Pauli Exclusion principle disallows any two identical fermions such as electrons to exist in the same quantum state. This electron degeneracy pressure is what supports against the further collapsing of the white dwarf stars.
Chandrasekhar Limit lines the minimum mass a white dwarf star must exceed to form a supernova explosion and end up as either a white dwarf or a black hole. This limit is determined to be roughly 1.4 times the mass of our Sun. For a long time, it was believed that the end state of all-stars is the white dwarf. In 1943, Indian Astrophysicist Chandrasekhar discovered the Chandrasekhar limit at which the star is massive enough that the force of gravity is greater than the electron degeneracy pressure.
More Massive Stars
A star whose core is so massive as to overcome the Chandrasekhar limit results in a titanic explosion called a supernova. Once observed, a supernova can outshine its parent galaxy as it has enough energy to be 10 billion times brighter than our Sun. Supernovae are responsible for the creation of most of the heaviest and precious elements as their shock waves produce enough energy for the fusion of elects heavier than iron.
After this Supernovae explosion of massive stars, two end states are possible.
Neutron Stars are stars having the mass of the Sun and the size of a city. Neutron stars are objects with the highest density in the observable universe. Neutron stars rotate approximately 600 times per second, and they have magnetic fields that are a million times stronger than Earth’s magnetic fields.
Stars ending their lives with more than three times the solar masses are giants that no degeneracy pressure can hold. Einstein’s general relativity can only explain black holes as the gravity around these objects are very large. The black hole has an information barrier known as the event horizon beyond which information cannot pass. This escape velocity of a black hole is greater than the speed of light, thus even light and other electromagnetic radiations might not escape a black hole. The Blackhole center’s singularity where any absorbed matter, including light, might collapse to zero volume.
Death of our Sun and Humanity on Earth
Our Sun’s death is not something we should be concerned about as it still has fuel left worth 5 billion years. However, humanity won’t probably be around even to witness the death of our own Sun. In about one billion years, the Sun will become hot enough to boil out all of Earth’s oceans. Our Sun’s brightness has been increasing by 10 percent every billion years, and this is enough to change the Goldilocks zone of the solar system. The goldilocks zone is a region where water can exist in a liquid state, making planets in that region habitable. In the next one billion years, our Earth might no longer be in this zone due to the increased temperature of our Sun. By this time, the Sun may have stopped fusion hydrogen fusion Mars will have replaced our Earth as the new habitable planet.