Red Dwarfs Will Be Humanity’s Last Home Before the Universe Dies - Beyond The World
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Red Dwarfs Will Be Humanity’s Last Home Before the Universe Dies

We could survive for millions of years around them if everything else went away.

The universe will be plunged into eternal darkness when the last star dies. That day is still a long way off, but it will arrive as certain as the sunrise tomorrow. The final star in the universe will most certainly be a red dwarf. Alien life forms could exist in the neighborhood of such a star, and it could be humanity’s final home before the cosmos becomes uninhabitable. What do we know about these mysterious red dwarfs? Should we start packing our belongings?

Red dwarfs account for almost three-quarters of all stars in the cosmos. However, their individual masses are merely a fraction of the mass of the Sun, making them the tiniest stars in the universe. They also don’t glow exceptionally brilliantly, thus they can’t be seen with the naked eye in the night sky. We can only see red dwarfs in our immediate vicinity, even with the most advanced technology. Red dwarfs account for around 50 of the 60 stars closest to our Solar System. They can be found anywhere.

A planet very closely oribiting its host star.
A planet orbiting a red dwarf (artist’s impression). Notice its proximity to the star. Source: Wikimedia Commons/ESO

All stars, including red dwarfs, convert hydrogen into helium. Red dwarfs, on the other hand, are convective, whereas other stars enrich helium in their cores. This means that hydrogen and helium are continually interacting with one another. As a result, it takes a very, very long time for their fuel to run out and they die. Red dwarfs, in fact, burn so slowly that they can live for up to 10 trillion years. An incalculable period of time. You could finally read all those masterpieces you’ve been meaning to read. Because the universe is only 13.75 billion years old, no red dwarf has progressed to an advanced state. The majority of red dwarfs are still in their infancy. Because the smallest red dwarfs can only just be defined as actual stars, the smallest star in the entire universe is likewise a red dwarf. A little less hydrogen and they would be brown dwarfs, failed stars with hardly any fusion processes going on in their cores.

I promised you aliens and a new home for humanity in the first paragraph. Where do these factors come into play? We will have to start looking for a new home at some point because our Sun will die one day (don’t worry, it will take a while). Aliens may not be far away where there are habitable planets. We discovered that at least half of all red dwarfs contain rocky planets with masses up to four times that of Earth using the Kepler satellite telescope. Many of them are even in the habitable zone, which is where water is liquid.

Red dwarfs, on the other hand, aren’t particularly hot, so a planet would have to get pretty close to them to be habitable. It is probably close to the distance between Mercury and the Sun. That appears to be a problem. The planet, for example, would most likely be tidally locked. That is, only one side would ever face the star. That side would become tremendously heated, while the other would remain forever frozen. These are extremely tough living circumstances. As a result, Merkur isn’t always the most popular vacation spot.

Oceans may be able to scatter some of the star’s heat, providing some equilibrium. Alternatively, and more concerningly, the red dwarf’s tidal forces may heat up the planet to the point that it loses all of its water. Such a planet, like Venus, would be a flaming pit of misery. It is also not a popular tourist site.

Unfortunately, the majority of red dwarfs have highly fluctuating energy outputs. They can be heavily coated in starspots, which can substantially limit their light over months. This has the potential to freeze entire oceans. Not only that, but solar storms can occur at any time, doubling the brightness of red dwarfs in minutes. Such storms have the potential to destroy a large portion of a planet’s atmosphere, rendering it uninhabitable. Not exactly optimal living conditions for demanding beings such as ourselves.

Red dwarfs, on the other hand, have a significant advantage in terms of lifespan. A fairly stable red dwarf might very possibly host a habitable planet. Life on Earth has existed for around 4 billion years, and we may have another billion years before the Sun becomes so hot that complex life forms cannot live on our planet. Then we’ll either die or have to find a new home. The clock is ticking.

A sunrise on a dark planet.
There will be a last sunrise. Even on a planet around a red dwarf. Source: Pixabay

A red dwarf might potentially provide humanity with sanctuary for trillions of years. A portion of the Milky Way’s red dwarfs may harbor habitable, Earth-sized planets. That equates to billions of potential houses. But we don’t even have to stop at Earth-like worlds. Red dwarfs may also be orbited by gas giants with suitable moons. Or by massive rocky planets, sometimes known as super-Earths. The number for viable human habitats quickly builds up. And it doesn’t even include the Milky Way.

Unfortunately, even a red dwarf must die at some point. The end of the final red dwarf in trillions of years will be unspectacular. As the hydrogen runs out, the red dwarf shrinks until it becomes a blue dwarf. When all of its fuel is depleted, it collapses into a white dwarf, which is as tiny as Earth and largely composed of dense gases such as helium-4 nuclei. Without any sources of energy, the ‘star’ cools very slowly over billions of years, eventually becoming a cold black dwarf. A depressing ending for the universe and humans. Everything we do, everything we are, all our offspring, and existence itself have an expiration date. Fortunately, it is still available.

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Robert Crosby
Robert Crosby
9 months ago

Stars are expected to form normally for 1–100 trillion years, but eventually the supply of gas needed for star formation will be exhausted. As existing stars run out of fuel and cease to shine, the universe will slowly and inexorably grow darker. A minimum of a trillion years? That is an almost unimaginable time, virtually infinite in terms of human existence.

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