Saturday, January 7, 2023


Every one of you in your life will surely have had a chance to admire a picture of the Andromeda galaxy.

The Andromeda Galaxy, or M31, is currently 2.53 million light years from the Milky Way. This distance is not fixed: both the Milky Way and M31 move in space.

The observations carried out with the Hubble Telescope allowed to establish with great precision the motions in space of the two galaxies and to determine their future evolution. It turned out that the Milky Way and the Andromeda Galaxy are approaching and it is very likely that in the future, in about 4-5 billion years, they will collide.

But don't worry: a collision between galaxies doesn't mean the Earth will be The distance between the stars is in fact so great that it is highly unlikely that the stars of the two galaxies collide destroying each other.

The collision, however, will profoundly change the structure of the two galaxies: the Milky Way and M31 in fact will merge to form a single giant elliptical galaxy, whose nucleus will replace the luminous wake of the Milky Way in the sky.

The post image is an artistic representation of what could happen. The first panel shows the current situation.

The second shows how the size of the Andromeda galaxy will obviously increase from Earth in two billion years. In the third image, in 3.75 billion years, M31 will be big enough to cover most of the sky. The fourth and fifth panels show the beginning of the collision in 3.9 billion years. In the sixth image the shape of the two galaxies is now unrecognizable compared to the beginning of the collision. The end of fusion is shown in the seventh and eighth rows: the Milky Way and M31 have become one elliptical galaxy.

Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas, and A. Mellinger.

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