The Andromeda galaxy, the closest spiral galaxy to the Milky Way, is not visible in the night sky unless it is sought for.

Milky Way and Andromeda have begun to combine.

In the absence of optical aid, however, it is only discernible as a fuzzy patch of light in the night sky. In the distant future, though, Andromeda will glow brightly in our sky, becoming larger as it approaches. The eventual merging of our two galaxies has already begun, despite the fact that they are currently separated by 2.5 million light-years.

The Andromeda galaxy is now approaching our Milky Way at around 70 miles per second (113 kilometers per second). Consequently, our merger will take place five billion years from today. In August of 2020, however, the peer-reviewed Astrophysical Journal revealed fresh evidence indicating that the collision between our galaxies had actually begun.

The news regarding the Andromeda galaxy originated from Project AMIGA, which utilizes the Hubble Space Telescope to examine the Andromeda galaxy’s environs in deep space. Absorption Map of Ionized Gas in Andromeda is abbreviated as AMIGA.

The Andromeda galaxy, our Milky Way, and other galaxies are surrounded by a huge envelope of gas, dust, and stray stars known as a galactic halo. The halos of galaxies are faint, so faint that finding them is a difficult task. These researchers determined the extent of the Andromeda galaxy’s halo by measuring how much light it absorbed from background quasars. They were shocked to discover that the Andromeda galaxy’s halo extends beyond its observable borders by a vast distance.

In fact, it stretches half the distance to the Milky Way (1.3 million light-years) and beyond in other directions (up to 2 million light-years).

Does this then imply that the halos of the Andromeda and Milky Way galaxies are in contact?

From our vantage point within the Milky Way, it turns out that we cannot readily measure the features of our galaxy’s halo. Due to the identical size and appearance of the two galaxies, astronomers hypothesize that the Milky Way’s halo would likewise be similar.

In other words, it appears that the weak halos of the galaxies have indeed begun to interact. Therefore, in a sense, the collision between our two galaxies has already begun.

NASA provided the below photographs in 2012. They are artists’ interpretations of what a person on Earth could observe as the Andromeda galaxy hurtles towards us.

The images below are based on Hubble Space Telescope measurements of the Andromeda galaxy’s velocity and computer simulations of their ultimate collision. In addition, a series of studies released in 2012 demonstrated that our Milky Way galaxy and the Andromeda galaxy would combine to create a single large elliptical galaxy, or football-shaped galaxy, as opposed to sometimes glancing off each other.

In February of 2022, Roeland van der Marel, an astronomer at the Space Telescope Science Institute, told Discover Magazine:

Whether the impact is head-on or more of a glancing blow has little effect on the outcome.

This is a brand-new, enormous elliptical galaxy.

However, the Milky Way and Andromeda will not be the only galaxies engaged in this merger. As depicted in the movie below, M33, also known as the Triangulum galaxy, the other massive galaxy in our Local Group of galaxies, will also play a part.

The Triangulum galaxy is the smaller object between the Andromeda and Milky Way galaxies in the movie below. Despite the likelihood that the Triangulum galaxy will not join the merger, it may at some time collide with the Milky Way while engaged in a cosmic dance with the two bigger galaxies.

In the entirety of the cosmos, galaxies are colliding. With the assistance of sophisticated telescopes, astronomers watch galactic collisions and their aftermaths. When two galaxies merge, they are in some respects similar to ghosts; they just pass through one another. Because stars inside galaxies are separated by such vast distances, this is the case. Therefore, stars do not generally collide when galaxies merge.

Thus, the merger will influence the stars in both the Andromeda galaxy and our Milky Way. The Andromeda galaxy has around a billion billion stars. The Milky Way contains around 300 billion stars. Both galaxies’ stars will be placed in new orbits around the newly fused galactic core.

According to experts who participated in the 2012 study, the sun will likely be blasted into a new sector of our galaxy.

However, they stated, “the Earth and solar system are not in risk of destruction.”

How then is life on Earth? Will life on earth survive the merger? In around 7.5 billion years, the sun will become a red giant, at which point it will expand and engulf the Earth. But even before to then, the sun’s luminosity or inherent brightness will grow. This will finally occur in around four billion years.

As solar energy reaching the Earth rises, the temperature of the Earth’s surface will rise. We may see a greenhouse effect comparable to that occurring on the neighboring planet Venus. Therefore, there is a significant chance that terrestrial life will be extinct when the union is complete.

However, by that time, perhaps some earthlings will have achieved space travel. Perhaps we will have abandoned the planet and our solar system. Andromeda’s collision with the Milky Way may still be seen, but from a slightly altered viewpoint.

The merging between the Milky Way and Andromeda has already begun. In 5 billion years, the two spiral galaxies will merge into one enormous elliptical galaxy.