The Andromeda Galaxy is a colossal tangle of around one trillion stars that lies next to the Milky Way. However, it will collide with our galaxy billions of years in the future.

On a clear night away from city lights, if you gaze toward the constellation Andromeda, you can just make out the Andromeda Galaxy, a long, fuzzy blob.

The Andromeda Galaxy, often known as M31, is the nearest large galaxy to the Milky Way, despite being 2.5 million light-years away. This makes it the furthest object typically visible with the naked eye.

Some believe that the Andromeda Galaxy contains around a trillion stars. And its diameter exceeds two hundred thousand light-years. This is considerably larger than the Milky Way, which, according to more recent estimates, is 150,000 light-years in diameter (however it is difficult to determine where either galaxy “ends”). Our galaxy appears to have between one-fourth and one-half as many stars as the Andromeda galaxy, while astronomers are still trying to establish a precise count.

The Andromeda Galaxy was discovered when.

Many thousands of years ago, individuals who glanced up at the sky likely pondered what this fuzzy area was. In 964 A.D., a Persian astronomer named Abd al-Rahman al-Sufi discovered the Andromeda Galaxy while writing a book titled “Fixed Stars.” In it, he identified Andromeda and the position of the Large Magellanic Cloud, a dwarf galaxy that circles the Milky Way. The Andromeda Galaxy was sometimes referred regarded as a “small cloud” in the sky.

Astronomers did not begin to recognize Andromeda’s uniqueness until the 1800s. Until approximately a century ago, scientists believed that the Milky Way was the whole cosmos.

Observers use telescopes to search for comets have observed “nebulae” for some time. This was a word for any fuzzy nighttime object that was not a comet. The nebulae that resembled Andromeda and had a spiral form were spiral nebulae. However, in 1864, an English astronomer called Sir William Huggins used a prism to isolate and investigate the distinct hues of light emitted by various nebulae. Huggins saw that M31’s light was substantially different from that of other nebulae as a result of his actions.

The great argument over the universe’s galaxies.

Over the subsequent decades, further astronomers noted the occurrence of supernovae in Andromeda. Astronomer Heber Curtis utilized the known brightness of these explosions to calculate the distance to Andromeda. He believed that these “spiral nebulae” was a staggering 500,000 light-years distant, which would place it well beyond our Milky Way.

A few years ago, Vesto Slipher, an astronomer at the Lowell Observatory in Flagstaff, focused the 24-inch Clark Telescope toward M31 and discovered that it was rushing toward us at an incredible rate. Slipher measured almost a dozen other spiral nebulae, of which all but three were traveling away from the Earth. His evidence demonstrated that Andromeda was not in the Milky Way galaxy. It inhabited the outdoors. This was the first convincing evidence that the cosmos is expanding.

These results were among the initial statements made by Curtis and Harlow Shapley during the renowned “Great Debate” (the latter an ambitious young scientist). Numerous scholars concurred with Shapley’s long-held belief that the Milky Way represented the cosmos. However, the data suggested that Andromeda and other strange spiral nebulae were in fact “island universes.” It would take years to determine who was correct.

In a billion billion years, the night sky will be filled with stars, dust, and gas from the Milky Way and the nearby Andromeda Galaxy (M31).

Lynette Cook for Astronomy magazine

Milkomeda happens when the Milky Way and Andromeda meet.

We now know for sure that the Andromeda Galaxy is a separate universe from our own. But it won’t be like this forever. Slipher’s observations first showed that the Milky Way and Andromeda will get too close to each other in about five billion years. They will hit each other with sideways blows, ripping stars off of each other to make long, drawn-out tails.

When these events happen, the Andromeda Galaxy will be a big part of the night sky here on Earth. But when the two finally get completely tangled up, they will merge into one huge group of stars. But the final object will not be a spiral galaxy. Instead, it will be an elliptical galaxy. Astronomers call this future galaxy Milkomeda, and galaxy mergers like this are very common.

But even though it might seem like a collision between two galaxies could only cause destruction, galaxy mergers often lead to huge amounts of new stars being made. Even though humans probably won’t live long enough to see it, this too will be visible from our solar system.

Still, the Milkomeda crash will cause a lot of bright, new stars to appear in the night sky. So, this fight between galaxies won’t kill either of them. Instead, the galaxies might even get new life from the mergers.