The artist’s concept of a red giant star burning a planet in orbit around it. Image via ESO / L. Calçada.
The earth exists thanks to our sun, which formed 4.5 billion years ago in an orbit around a large cloud of dust and dust in space. Similarly, the sun will destroy the earth for living things, about 5 billion years from now. As the sun evolves, it will expand to a red giant star and fry our planet to a can. What’s more, the death of the Earth will take place against a background of change on a galactic scale. Our Milky Way galaxy and the Andromeda galaxy will be in the midst of a colossal collision that will change our galactic home in space forever.
Our sun is a G-star that is currently about halfway through its life cycle. This type of star is very stable for most of its life, melting hydrogen silently in helium inside it for billions of years. One day, the hydrogen inside the sun will run out. At that point, the inward pressure of gravity will be overcome by the outward pressure of the internal fusion of the sun until the sun becomes enough to melt helium. At that point, the sun will balloon outward to become a red giant star.
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As the sun warms and expands, its outer layers will envelop the inner planets, Mercury and Venus. The outside of the sun will reach approximately the orbit of the earth. Our planet’s water and atmosphere will boil away and leave nothing but a charred, lifeless rock. Mars will take a while to warm up, but eventually Mars will also be outside the habitable zone for humans. At that point, the moons of the outer planets – such as Jupiter and Saturn – will be the only places in our solar system for human colonies.
But even these places will be only temporary solutions in the search for a new home.
As our sun expands to the red giant phase, the habitable zone around it will be pushed outward into the solar system. Image via NASA / Wendy Kenigsburg.
The red giant phase of the sun may still last about a billion years, but eventually the helium will also run out. Then the sun will blow off an envelope of gas. Astronomers peering through telescopes into other galaxies will see our sun as what we call a planetary nebula, a large gas shell that surrounds a dying star. Eventually the shell will disappear into space, and what is left of our sun will become a white dwarf star.
Earth’s astronomers can look into space to see the Earth’s future. For example, 400 light-years away, a star known by astronomers as SDSS J1228 + 1040, is a white dwarf with its funeral envelope in the gas nebula, in which astronomers have found the signature of a planetary animal still around its home. orbits, long after its disastrous sun. death.
And what about the Milky Way system itself, the great island stars that contain our earth and sun? By the time our sun enters the red giant phase – long before it sits like a white dwarf – the Milky Way itself will undergo a long process of inevitable collision with the giant spiral system next door, the Andromeda galaxy. The last people on earth – if there are still a few billion years left – the Andromeda galaxy will grow bigger and brighter in the night sky. It is currently barely visible to the naked eye from a dark sky. But a few billion years from now, the Andromeda galaxy will be a breathtaking, unmistakable swirl of stars easily visible in the night sky of all Earth’s inhabitants.
As Andromeda and the Milky Way move closer together, the great mass of the Andromeda galaxy will affect the stars in our Milky Way. Our galaxy is wide and flat, like a pancake. We on earth currently see its stars on a dark August evening as a large hazy band across the sky. But as the seriousness of Andromeda distorts their paths, the stars of the Milky Way will be scattered through our sky.
It looks incredible, but stars in galaxies are so far apart that even when the two giant spirals collide, there will be few fireworks of collisions between stars. However, gas clouds in the two galaxies are likely to collide and form large numbers of new stars.
This series of illustrations shows the predicted merger between our Milky Way system and the adjacent Andromeda system. Image via NASA.
Eventually, the Milky Way and Andromeda galaxies will settle to form a new massive lumpy galaxy. At this point, the earth, our sun, and the rest of our solar system may be in a whole new place with respect to the galactic center. At present, the earth lies about 25,000 light-years from the center of the Milky Way. After Andromeda and the Milky Way merged, astronomers believe that our house in space will have been ripped out into a new galactic orbit, about 100,000 light-years from the center of the new, large Andromeda-Milky Way combo system. As theorist TJ Cox of the Harvard-Smithsonian Center for Astrophysics put it:
You could say that we are being sent to a nursing home in the country.
And what will be the fate of mankind? It is impossible to say. If it survives, the future of mankind will depend on our ability to travel away from our dying sun and camp elsewhere.
Fortunately, we have several billion years to figure out how we can accomplish this monumental task.
In short: What will be the Earth’s fate? The earth is likely to become a dry, scorched rock as our sun becomes a red giant star. What’s more, the sun and the earth (and the rest of our solar system) are expected to be thrown out of the Milky Way and Andromeda galaxies, away from the galactic center, to the outskirts of a new large galaxy that occurred during the collision. .
