Earthlings still have about a couple of billion years before the oceans boil and the planet becomes uninhabited. The sun will heat up, swell to the size of a red giant, melt helium in its core, then eject the outer layers and turn into a white dwarf. But new stars will appear and shine, and our galaxy will be alive and prosperous.
But even the Milky Way will one day cease to exist: at first it will cease to be the way we know it, and then it will disappear completely.
The story of the death of our galaxy begins right here and now. The Galactic Local Group, which includes the Milky Way, also includes the Andromeda galaxy and several smaller galaxies. Let's get to know them better.
The Triangulum Galaxy is equal to 5% of the mass of the Milky Way. It is the third largest galaxy in our group. The galaxy has satellites, and it itself is a satellite of the Andromeda galaxy.
Galaxy Triangle.
The Large Magellanic Cloud weighs 1% of the mass of the Milky Way. It is very close to us - only 200 thousand light years away. The galaxy is undergoing a stellar baby boom.
The Small Magellanic Cloud galaxies, NGC 3190 and NGC 6822, weigh between 0.1% and 0.6% of the mass of the Milky Way.
Elliptical galaxies M32 and M110 are satellites of the Andromeda galaxy, but their masses are greater than those of the galaxies described above.
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Our group also includes 45 more small galaxies. Each has a dark matter halo around it; each of them is gravitationally related to the other.
Galaxies interact gravitationally. This is not only about gravitational attraction, but also about tidal. What it is? When a part of a small galaxy that is closer to a large galaxy is attracted by strong gravitational force, the part that is farther away will experience less gravitation. As a result, small galaxies are stretched and eventually torn apart.
The small galaxies that make up our local group - both the Magellanic Clouds and all the dwarf elliptical galaxies - will explode in this way. Their substance will fall into large galaxies
What happens next? In 4 billion years, the mutual gravitational attraction of the Milky Way and Andromeda will drag us into a dance that will lead to the merger of two huge galaxies. The process will take billions of years, the spiral structure of both galaxies will be disrupted, resulting in a single giant elliptical galaxy at the center of our local group: Milkdromeda. This same galaxy will eventually absorb other galaxies of our local group.
Until galaxies disappear, their stars will continue to live. Long-lived stars will burn their fuel for more than 10 trillion years, and new stars will be born from gas, dust and stellar corpses, but in smaller and smaller quantities.
Even when the last star burns out, white dwarfs and neutron stars will continue to shine for hundreds of trillions or even quadrillions of years. When they inevitably go out, we still have brown dwarfs that will shine for tens of trillions of years.
When the last star burns out, there will still be galactic mass and a supermassive black hole at its center. In the center of Milkdromeda, this object will be equal in mass to 100 million of our Suns.
A lonely black hole and matter around it.
Simulated black hole evaporation.
Thanks to the Hawking radiation phenomenon, the black hole will also die. It will take 10 ^ 80 and 10 ^ 100 years. There will be only a halo of dark matter, which will later dissipate by itself. When there is no substance inside, what was once the galaxy of the Milky Way will disappear forever.