The Andromeda galaxy is our closest large galactic neighbor, located approximately 2.5 million light-years away. It is currently on a trajectory that will lead to a future galactic collision with our galaxy. This cosmic event will unfold over billions of years, gradually transforming the night sky as seen from Earth.
Andromeda’s Current Appearance
Today, the Andromeda galaxy appears as a faint, fuzzy patch of light. Under dark, moonless conditions, it is visible to the unaided eye. Its apparent magnitude is around 3.4, making it one of the brightest objects beyond our galaxy that can be seen without optical aid.
Despite its faintness, Andromeda’s apparent size is significant, spanning about 3 to 4 degrees across the sky. This is roughly six to eight times the apparent diameter of the full Moon. What is seen by the naked eye is primarily its brighter central region, with its full extent only revealed through long-exposure photography or telescopes.
The Approaching Galactic Collision
The Andromeda galaxy is approaching the Milky Way at about 110 kilometers per second. In approximately 3.75 billion years, Andromeda’s gravitational pull will begin to distort and stretch both galaxies.
As Andromeda draws nearer, its disk will appear progressively larger. Around 2 billion years from now, it will be noticeably bigger, and by 3.75 billion years, it is predicted to fill a significant portion of the field of view. The initial “collision” will not involve stars directly hitting each other due to the immense distances between them, but rather a gravitational dance that reshapes both galaxies. This process will continue for millions of years, transforming the familiar night sky.
Visuals During the Galactic Merger
The most significant visual changes will occur during the active merger phase, around 3.85 to 4 billion years from now. The sky will become “ablaze” with brilliant new star formation. This intense star birth is ignited by the compression of gas and dust clouds as the two galaxies intermingle.
Chaotic streams of stars, gas, and dust will become prominent as the two galaxies distort each other. Computer simulations suggest multiple galactic nuclei might be visible as the central regions of the Milky Way and Andromeda coalesce. The night sky will be dominated by these swirling structures and bright nebulae.
The New Galactic Landscape
After billions of years of gravitational interaction, the Milky Way and Andromeda galaxies will fully merge. This process is expected to conclude around 6 to 7 billion years from now. The two spiral galaxies will then form a new, larger elliptical galaxy, informally termed “Milkomeda” or “Milkdromeda.”
The night sky will eventually be dominated by this new, more spherical galaxy. The distinct spiral arms of the original galaxies will be gone, replaced by a more uniform, diffuse glow. Billions of stars will populate this new galactic structure.