Artist’s concept of a red giant star scorching a planet orbiting around it. Image via ESO / L. Calçada.
Earth exists because of our sun, which orbited it 4.5 billion years ago by a huge cloud of gas and dust in space. Likewise, the sun will ruin the earth for living things in about 5 billion years. As the sun evolves, it will expand to become a red giant star and burn our planet to a cinder. In addition, Earth’s death will occur against a backdrop of galactic-scale changes. Our Milky Way Galaxy and the Andromeda Galaxy will be in the middle of a colossal collision that will forever change our galactic home in space.
Our sun is a G-type star that is currently about halfway through its life cycle. This type of star is very stable for most of its life, quietly melting hydrogen into helium within billions of years. One day the hydrogen inside the sun is exhausted. At that point, the inward pressure of gravity will win over the outward pressure of the sun’s internal fusion, until the sun warms up enough to fuse helium. At that point, the sun will balloon out to become a red giant star.
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As the sun warms and expands, the outer layers will envelop the inner planets Mercury and Venus. The outer edge of the sun will grow to roughly the Earth’s orbit. The water and atmosphere of our planet boil away, leaving nothing but a charred, lifeless rock. Mars will warm up for a while, 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 locations will only be temporary solutions in the search for a new home.
As our sun expands into the red giant phase, the habitable zone around it will be pushed out into the solar system. Image via NASA / Wendy Kenigsburg.
The red giant phase of the sun can last about a billion years, but eventually the helium will also run out. Then the sun will blow away an envelope of gas. Astronomers peering through telescopes in other galaxies will see our sun as what we call a planetary nebula, a large shell of gas surrounding a dying star. Eventually that shell will disappear into space, and what is left of our sun will become a white dwarf star.
Earth’s astronomers can look out of space to glimpse the future of Earth. For example, 400 light-years away, a star known to astronomers as SDSS J1228 + 1040 is a white dwarf with its gas nebula shroud, in which astronomers have found the signature of a planetesimal that orbits its home sun long after its disastrous orbit. death.
And what about the Milky Way itself, the large island of stars that contains our Earth and Sun? By the time our sun is ballooning into the red giant phase – long before it settles down as a white dwarf – the Milky Way itself will undergo a lengthy process of inevitable collision with the adjacent giant spiral galaxy, the Andromeda galaxy. The last people on Earth – if there are still humans in a few billion years – will see the Andromeda Galaxy grow bigger and brighter in the night sky. It is currently barely visible to the naked eye from a dark sky. But in a few billion years, the Andromeda Galaxy will be a breathtaking, unmistakable whirl of stars easily visible in the night sky of all Earth’s inhabitants.
As Andromeda and the Milky Way get closer together, the large mass of the Andromeda Galaxy will begin to affect the stars in our Milky Way. Our galaxy is wide and flat, like a pancake. We on Earth are currently seeing its stars on a dark August evening as a large blurry band in the sky. But as Andromeda’s gravity warps their paths, the stars of the Milky Way will scatter across our sky.
It may seem incredible, but stars in galaxies are so far apart that even when the two giant spirals collide, there will be little fireworks from star collisions. However, gas clouds in the two galaxies are likely to collide and form massive conglomerations of new stars.
This series of illustrations shows the predicted merger between our Milky Way Galaxy and the neighboring Andromeda Galaxy. Image via NASA.
Eventually, the Milky Way and Andromeda galaxies will settle down and form a new massive blob-shaped galaxy. At this point, the Earth, our sun, and the rest of our solar system may be in an entirely new location from the galactic center. Currently, Earth is about 25,000 light-years from the center of the Milky Way. After Andromeda and the Milky Way merge, astronomers believe our home in space will have torn outward to a new galactic orbit some 100,000 light-years from the center of the new large Andromeda-Milky Way combination. As theorist TJ Cox of the Harvard-Smithsonian Center for Astrophysics said:
You could say that we are being sent to a retirement home in the country.
And what will be the fate of humanity? It is impossible to say. If it survives, the future of humanity will depend on our ability to travel away from our dying sun and set up camp elsewhere.
Fortunately, we have a few billion years to figure out how to accomplish this monumental task.
In short, what will be the fate of the earth? The Earth will undoubtedly become a dry, scorched rock, as our sun becomes a red giant star. What’s more, as the Milky Way and Andromeda galaxies collide, our Sun and Earth (and the rest of our Solar System) are expected to be hurled outward, away from the galactic center, to the edge of a new large galaxy that is created during the collision. .
