- Every known star in the universe formed the age of star formation called the stellar age
- The universe will eventually use up its entire supply of star-forming material and star-forming will stop
- Several trillion years from now, the last star will burn out and only stellar remnants will remain
- The stellar remnants will cease to exist within several trillion years, leaving behind a universe full of radiation.
The universe has been around for 13.8 billion years, from the Big Bang until now. This may sound long, but the universe is still young compared to when it likely existed. It may seem strange, but the universe will one day cease to exist. Several trillion years from now, the stars themselves will burn out, leaving behind a trail of stellar remnants such as neutron stars, white dwarfs, and black holes. trillions and trillions of years after the last star burned out; Even stellar remnants will slowly decay until the universe contains nothing but an endless sea of radiation. When and how will this happen?
Our solar system and most of the stars we can all see formed during an era of cosmic history called the Interstellar Age. The stellar age is the period in which star formation occurs throughout the universe. This era began about a million years after the Big Bang and will continue for another hundred trillion years or so. Although 100 trillion years seems like a long time, the interstellar age will be one of the shortest eras of the universe. Given that the stellar age is defined as the age in which star formation occurs throughout the universe, its end is determined when star formation stops. The idea of stopping star formation altogether may seem strange, but it is inevitable given that the universe contains a limited amount of usable hydrogen. When stars use hydrogen for formation and evolution, they gradually fuse hydrogen into heavier elements. Eventually, all usable hydrogen will be incorporated into heavier elements, which means star formation will gradually slow down and then stop. More massive stars will be the first to blast off, as higher-temperature hydrogen fuses faster than lower-mass stars. Eventually, all the brightest stars in the universe will burn up in a supernova explosion. It will leave behind many stellar remnants such as neutron stars, pulsars, and black holes. Once all the high-mass stars transform into a supernova, all that will remain are the fainter, low-mass stars. Then the stars will be of medium size, like our sun. The last stars in the universe will be red dwarfs, whose rate of hydrogen fusion is so slow that they will continue to shine for many trillions of years after every other star burns out. Eventually, they will also burn until the last star in the universe ceases to exist. In about 100 trillion years, the universe as we see it will no longer exist, and yet the universe will be far from dead. Instead, stellar remnants will continue to provide some form of light, and planets will likely still exist around some neutron stars and white dwarfs. Moreover, rogue planets, worlds that do not orbit a star, will continue to drift through an empty, starless universe.
Before the last stars burn out, most galaxies in the universe will be located at such great distances from each other that it would be impossible to observe another galaxy from any other. The universe is constantly expanding and increasing in size. Because of the amount of dark energy in space, the rate of expansion is accelerating. As matter gets further and further apart, the force of gravity weakens, and space accelerates faster. Eventually, most objects will pass the so-called cosmic horizon, which means they will be too far away for their light to ever reach each other. Our cosmic horizon will gradually shrink until the nearest galaxy passes our cosmic horizon. The universe will still contain billions of stars and galaxies, yet it would be impossible to notice anything outside the galaxy in which you reside.
The stellar epoch will be one of the shortest in cosmic history when compared to the eras that follow. After the last of the stars burn out, all that will remain are stellar remnants. These include white dwarfs, neutron stars, pulsars, and black holes. It is also possible that some planets live beyond the interstellar age. Scientists have discovered planets orbiting neutron stars, so it is not an exaggeration to assume that some planets will either survive the death of their star or that some may form as a result of the death of their stars. Either way, some planets will remain in orbit around a stellar remnant long after the last of the stars have burned out. If some of these planets happen to retain a significant amount of internal heat, they could even possess subsurface oceans of liquid water, which may be the last place in the universe where life could exist. Eventually, though, even astral remnants would cease to exist. This era of cosmic history is known as the Degenerate Age, and is likely to last for hundreds of trillions of years. Although their lives are unimaginably long, even things like white dwarfs, neutron stars, and black holes will cease to exist. Black holes will be the last black holes, with the largest black holes having a lifespan that can extend up to 10^72 years (one followed by 72 zeros).
black hole era
How exactly does a black hole cease to exist? Stephen Hawking was the first to predict that black holes will slowly shrink over time and fade out of existence in the distant future. Hawking predicted that every black hole emits a stream of radiation called Hawking radiation. The amount of Hawking radiation that a black hole emits is related to the black hole’s surface area. The larger the black hole, the less Hawking radiation. Thus, the larger the black hole, the longer it takes for it to lose mass and shrink. It will take trillions and trillions of years for the most massive black holes to shrink and disappear, but it will happen one day. When the last black hole ceases to exist, all that will remain in the universe are particles and radiation aimlessly drifting through infinity. The end of the era of the black hole will begin in the era of darkness. How long this age will last depends on when the protons decay. Since the life expectancy of protons cannot be observed, scientists have to rely on estimates. Scientists currently estimate that the half-life of a proton is about 1.67 x 10^34 years. If this turns out to be true, the last protons will eventually decay into smaller particles, in this case pions and positrons. One day, even these particles will cease to exist. Once all known particles decay, the universe will end. All that will remain is an endless sea of empty space.