The Milky Way and the Andromeda Galaxy will collide. What will become of us?

With the naked eye, in some regions of the northern hemisphere of the planet, it is possible to see a luminous point in the shape of a spiral just below the Milky Way. This is Andromeda, a nearby galaxy about 2.5 million light-years away.

However, this difference in space has a date to end. In 4 to 5 billion years, this same galaxy, which is approaching, will collide with the Milky Way, of which our Solar System is a part and where the Earth is located.

This will happen because both attract each other, explains Rafael Christ Lopes, doctor of Cosmology and professor at IFMA (Federal Institute of Maranhão). “Andromeda has about 1 trillion stars and our galaxy has about 200 billion. Since they are the two most massive systems of the local group [composto por 54 galáxias]they undergo mutual gravitational attraction, that is, one attracts the other”.

The phenomenon was discovered for the first time in 2012 by NASA astronomers, using data from the Hubble telescope, while observing the movement of Andromeda, which is approaching more than 400,000 km/h.

A “merger” may be in progress.

A more recent discovery, from 2020, has even highlighted that the merging process between galaxies could already be underway because the ‘halos’ of Andromeda and the Milky Way are ‘touching’, according to research based on data from the Hubble Space Telescope Station and published by the journal Science.

The image of Andromeda

Image: Nicolas Lefaudeux/Insight Investment Astronomy Photographer of the Year

Halos are the gaseous atmospheres that can cause star formation. In Andromeda and the Milky Way, they extend for millions of light years around the center of each.

Nicolas Lehner of the University of Notre Dame and lead author of a study published in The Astrophysical Journal, pointed out that because of our location in the Milky Way, scientists cannot determine the depth of our galaxy’s halo. However, there is a high probability that the halos of Andromeda and the Milky Way are very similar, as the two look alike.

For these characteristics, it is believed that the halo surrounding the Andromeda galaxy (which measures about one million light years) is in fact colliding with the halo of the Milky Way, which represents the beginning of the merger.

The stars will not collide with each other

When the merger between the galaxies is in a more advanced state, it is estimated that a single giant elliptical galaxy will form, where new stars can form, just as the planetary systems of one galaxy can join the other.

However, despite the ‘collision’ name, what will happen shouldn’t have a direct impact between the celestial bodies of the two, such as stars. According to Thiago Signorini Gonçalves, an astronomer at the Federal University of Rio de Janeiro, it will be just a merger of galaxies into one.

Galaxies are mostly empty space. They collide due to gravity, but the stars themselves won’t collide with each other. It’s like two clouds of mosquitoes meeting, but the mosquitoes don’t strike. Thiago Goncalves (UFRJ)

The solar system will change position

The Solar System is unlikely to be at risk of being destroyed by merging galaxies due to the huge gaps between stars, but there will certainly be impacts.

Studies indicate that our Sun and the entire system would be moved, occupying a new region in space. Rafael Cristo (IFMA)

It is also possible that the approximation between the galaxies pushes the Solar System away into an isolated region of the Milky Way, or transfers it to the territory of Andromeda’s invasion.

In about 5 billion years, shortly after the collision, the Sun will transform into a red giant and engulf our planet, according to predictions. So our fate is already ‘sealed’ in the Solar System.

How will this affect humans?

If humans still exist as we know them, the collision of galaxies will change the night sky a lot in the first place, causing a mess of the positions of the stars.

“Precisely because the stars will not collide with each other, the impact on the Earth, in principle, would be negligible. The stars in the sky will be very different because they will all be ‘messy’. The important thing for the Earth is to be close to the Sun , and which would probably continue like this, even after the collision with Andromeda”, underlines Thiago Signorini.

Detailed map of the Milky Way - ESA - ESA

Detailed map of the Milky Way

Image: ESA

black hole threat

After the galaxies meet, another possible phenomenon could arise due to the approximation between Andromeda’s nucleus and the Milky Way, presenting three possible futures for the Solar System, according to Thaisa Storchi Bergmann, a graduate professor at the Institute of Physics of the ‘UFRGS (Federal University of Rio Grande do Sul) and member of the World Academy of Sciences.

The key point is that Andromeda and the Milky Way have a supermassive black hole at their core, which will collide, and the gas inside galaxies can be captured by black holes through an accretion disk, where the gas rotates very fast, it heats up to hundreds of thousands of degrees, causing an intense glow and release of energy.

This would form one or even two quasars at the center of the “Andromeda-Milky Way” merger.

The orbit of the Sun would then be altered, and subsequently, the entire Solar System (Earth included) could end up near one of the supermassive black holes, which would bring tragic consequences to our blue planet, according to astrophysicists, who in 2018 they received the National Medal of Scientific Merit for their work in the study of black holes supermassive and their interaction with galaxies.

  • The Earth and the Sun can be close to a quasar and receive intense X-ray and ultraviolet radiation;
  • Both can be ejected from the galaxy by orbital energy transfer;
  • Captured and destroyed by black holes.

But will the Earth exist until then?

Professor Thiago recalls that the future of our species in astronomical terms is interesting, but today there are more pressing issues that man must solve if he wants to be present in the next stages of the galaxy.

You have to think about how humans will treat the Earth in the next billion years. Who knows if, with global warming and all the pollution problems, we will be able to preserve the Earth. Thiago Signorini (UFRJ)

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