Milkdromeda: Powerful Collision of Andromeda and the Milky Way

Milkdromeda: Powerful Collision of Andromeda and the Milky Way
Posted on: July 28th, 2023

The Andromeda Galaxy, a cosmic behemoth in its own right, is on a collision course with our home galaxy, the Milky Way. This colossal clash, predicted to occur billions of years from now, will ultimately result in the formation of an even larger galaxy, humorously dubbed ‘Milkdromeda’.

Andromeda is significantly larger than the Milky Way. It stretches across an impressive 152,000 light-years, dwarfing our galaxy’s diameter of around 100,000 light-years. Besides its remarkable size, Andromeda is also a barred spiral galaxy, a type characterized by a central bar-shaped structure composed of stars. It’s believed to possess a staggering mass equivalent to one trillion of our suns, a testament to its immensity.

This leviathan of a galaxy is currently rushing toward us at an astonishing speed of 70 miles per second. But there’s no need for alarm; the imminent celestial collision is not expected for several billion years.

The Andromeda galaxy, despite its considerable distance, can be observed with the naked eye from Earth. It’s a remarkable sight, appearing as a large, slightly nebulous star in the night sky. October presents the best opportunity for observation, when, from the vantage point of the northern hemisphere, it looms high overhead on clear nights.

Among the myriad celestial bodies visible to us, Andromeda holds a unique distinction. It is the most distant object that can be seen with the naked eye, and as it continues its approach, it will only become more conspicuous in the night sky.

For those interested in locating Andromeda or any other celestial object, smartphone applications can be a valuable tool. Personally, I find ‘Sky Map‘ to be a highly useful app on my Android devices. For those using Apple devices, ‘SkyView‘ is a commendable alternative. These applications can help guide your gaze to the right part of the sky, enhancing your stargazing experience.

Galaxy Collisions

The image depicted below was captured by the Gemini North Telescope, stationed in Hawaii. It reveals the dramatic dance of two galaxies, NGC 4568 and NGC 4567, as they are in the midst of a cosmic collision, gradually merging to form a single, larger galaxy. This powerful image serves as a stark reminder of the eventual destiny of our own galaxy, the Milky Way, which is predicted to collide with the Andromeda Galaxy billions of years from now.

Although the prospect of galactic collision might seem catastrophic, it’s important to note that galaxies are predominantly composed of empty space. Therefore, direct collisions between individual stars within the galaxies will be exceedingly rare. However, the gravitational interactions involved in these cosmic encounters can have significant effects on the bodies within the galaxies.

Planetary systems, for instance, might experience shifts in their orbits as a result of these gravitational disturbances. Some planets could be sent on entirely new paths around their host stars, while others may be ejected completely from their original orbits when other stars pass too close. This galactic merger, while largely non-violent in terms of star collisions, could result in a dramatic reshuffling of the cosmic order within the affected galaxies.


As the Andromeda Galaxy continues its inexorable approach towards the Milky Way, the two cosmic entities will not immediately merge. Instead, they will engage in a celestial dance, passing by each other multiple times in a kind of cosmic ballet. This intricate interplay will persist for billions of years before the two galaxies finally merge into one.

At the heart of this merger, the supermassive black holes residing in each galaxy will gradually spiral towards each other, their immense gravitational forces pulling them closer until they ultimately combine into a single, even more massive black hole.

The resultant galaxy, named ‘Milkdromeda’ in a playful nod to its progenitors, will be of an elliptical shape. This configuration is typical of merged galaxies, where the distinct spiral structures of the original galaxies have been disrupted by the gravitational forces at play.

The Milky Way and Andromeda are part of a larger cosmic structure known as the Virgo Supercluster, our local group of galaxies. Looking even further into the future, scientists speculate that around 100 billion years from now, the Milkdromeda galaxy could itself merge with other nearby galaxies within this supercluster. The outcome of this process would be a gargantuan supergalaxy, marking another significant milestone in the evolution of our cosmic neighborhood.

While we can only imagine what such a spectacle might look like, it’s a humbling thought. If any observers are still around to witness Milkdromeda, they would be privy to a truly awe-inspiring display of the universe’s grandeur and the dynamic nature of cosmic evolution.

Don’t hold your breath

Despite the startling speed of 70 miles per second at which Andromeda is moving towards us, it’s crucial to remember the sheer scale of space. Given the vast distance between our galaxies, it will still take approximately 5 billion years for Andromeda to make its rendezvous with the Milky Way.

As Andromeda continues its approach, it will grow increasingly larger and more prominent in our sky. Just 1 billion years from now, its spiral arms will be a dazzling sight, a celestial masterpiece painted across the heavens. This spectacle will serve as a reminder of the cosmic dance that our galaxy is engaged in, and the ever-changing nature of the universe itself. Milkdromeda is but a tiny piece of the galactic puzzle.

Death of the sun

Interestingly, the Milkdromeda collision coincides with a critical juncture in the lifespan of our own star. Around the same time, our sun, having exhausted its hydrogen fuel, will start to evolve into a red giant. This transformation will cause it to expand dramatically, potentially to the point where it engulfs the Earth. This expansion will lead to a dramatic increase in the sun’s luminosity, causing surface temperatures on Earth to rise and rendering our planet uninhabitable.

By then, humanity, if it survives, will hopefully have found refuge among the stars, establishing a new home on a distant planet in another corner of the galaxy. Yet, even as we confront the death throes of our sun, the night sky will offer a sight of unparalleled beauty.

Studying Messier 31

Andromeda, also designated as Messier 31, is close enough to us that the newly launched James Webb Space Telescope (JWST) can resolve its individual stars for detailed study. Among the countless stars within Andromeda’s sprawling spiral arms, there are approximately 229 Red Giant stars. These stars are in a late stage of stellar evolution, having exhausted their primary hydrogen fuel and now burning helium in their cores.

Star formation is a vital process in the evolution of galaxies, and studying Andromeda, our closest galactic neighbor, can provide invaluable insights into the history and future of our own Milky Way. In particular, Red Giants, as older stars, serve as cosmic time capsules. By determining their age, we can uncover clues about the timeline of galaxy formation and evolution.

Spectroscopy, a powerful tool in the astrophysicist’s toolkit, allows scientists to analyze the light emitted by these stars. By splitting the star’s light into its component colors, much like a prism creating a rainbow from sunlight, scientists can identify the elements present in the star. Each element leaves a unique signature in the spectrum, allowing researchers to determine the star’s composition.

This information can provide crucial insights into the star’s life history and the processes that have occurred within it. Such knowledge can help us understand the broader narrative of stellar evolution and the role these stars play in the grander scheme of galaxy formation and evolution.

Stars Age

The first generation of stars, known as Population III stars, were composed almost entirely of hydrogen and helium, the simplest and most abundant elements in the universe. Over time, these stars began to forge heavier elements within their cores through the process of nuclear fusion. Upon their death, these stars exploded in supernovae, dispersing these heavier elements into the cosmos. These elements were then incorporated into subsequent generations of stars and planets, enriching the universe with the diversity of elements we observe today.

By analyzing the elemental composition of a star through spectroscopy, scientists can infer its age. This is because the presence of certain heavier elements indicates that the star is a part of a later stellar generation. I delve deeper into this fascinating process of stellar nucleosynthesis in my article titled “Star Stuff“.

Spectroscopy has also opened new avenues in the search for exoplanets, planets orbiting stars outside our own solar system. When an exoplanet transits, or passes in front of its host star, some of the starlight filters through the planet’s atmosphere. By analyzing this filtered light, scientists can determine the chemical composition of the exoplanet’s atmosphere, gaining valuable insights about the planet’s potential habitability. I’ve discussed this captivating subject in greater depth on my dedicated exoplanet page. I invite you to spare a few minutes to give it a read.

Common Questions

These are some common questions folks have about Milkdromeda. It’s easy click bait to try and scare people but the truth is we have nothing to worry about but the Milkdromeda collision is still fascinating to ponder.

What is a Milkdromeda?

“Milkdromeda” is a humorous term coined by astronomers to refer to the future, larger galaxy that will be formed when the Milky Way and the Andromeda galaxies collide and merge. This event, although it sounds dramatic, is predicted to occur approximately 5 billion years from now. The result will be a massive elliptical galaxy, quite different from the spiral shape of both current galaxies. Despite the name suggesting a cataclysmic event, the vast distances between individual stars mean that direct collisions will be rare during this galactic merger.

Will Earth survive Andromeda collision?

The anticipated collision between the Milky Way and Andromeda galaxies is not expected to have a direct impact on our solar system or the Earth due to the vast distances between individual stars in each galaxy. Even though the galaxies themselves will collide, the chances of individual stars (and their associated planets) colliding is exceedingly small.

Is Andromeda bigger than Milky Way?

Yes, the Andromeda Galaxy is indeed larger than the Milky Way. Andromeda is estimated to be about 220,000 light-years in diameter, whereas the Milky Way is about 100,000 light-years across.
In terms of mass, the two galaxies were once thought to be about equal, but more recent measurements suggest that Andromeda could be as much as two to three times more massive than the Milky Way.

What happens when 2 galaxies collide?

When two galaxies collide, a process known as a galactic merger, it’s more like an intricate dance than a cataclysmic collision. The vast distances between individual stars mean that direct star-to-star collisions are extremely rare. Instead, the most significant changes are brought about by the immense gravitational forces at play.

Gravitational Interactions: As the galaxies approach each other, their mutual gravitational pull can distort their shapes, often leading to the formation of tidal tails – long streams of gas and stars pulled away from the galaxies.

Star Formation: The collision can cause the gas in the galaxies to compress, leading to a period of intense star formation, known as a starburst. This can cause the galaxies to shine brightly in infrared light.

Black Hole Activity: The supermassive black holes at the centers of each galaxy can be stirred into action, accreting more material and shining brightly as active galactic nuclei. Over time, these black holes will likely merge.

Formation of a New Galaxy: Over billions of years, the two galaxies will merge completely, their stars moving into new orbits to create a single, larger galaxy. The type of the resultant galaxy depends on the properties of the merging galaxies but could potentially be an elliptical galaxy or a large disk galaxy.

Potential Solar System Displacement: For individual solar systems like ours, a galactic collision could potentially lead to displacement. The gravitational effects might nudge our solar system into a different orbit around the galactic center or even eject it entirely.

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