Something extraordinary has just happened: the James Webb Telescope received an alarming signal from the Andromeda Galaxy, leaving scientists completely baffled.
The Expansion of the Universe and Our Relationship with Andromeda
The universe is constantly expanding, but it's not the
cosmos that's growing, but space itself. This phenomenon, known as "galaxy
escape," was first observed in the 20th century. However, there are
exceptions: nearby star systems, like the Andromeda Galaxy, are not moving away
from us, but are heading toward a direct collision with our Milky Way.
Andromeda, located about 2.5 million light-years away, is the closest galaxy to our own and can be observed with the naked eye under optimal conditions. Its spiral structure and star clusters share many similarities with the Milky Way.
Physical Characteristics of the Andromeda Galaxy
The Andromeda Galaxy, also known as M31, has dense areas of dust where new stars are born and hundreds of globular clusters in its outer regions. At its core, it harbors a supermassive black hole with a mass billion times that of the Sun, surpassing that of our own galaxy.
Its galactic halo, a vast spherical region surrounding the stellar center, extends for more than a million light-years, cementing it as the most prominent member of the local group of galaxies.
- Estimated total mass: between 0.7 and 2.5 trillion solar masses
- Stars: approximately 100 billion
- Comparison to the Milky Way: 1.5 trillion solar masses
From Nebula to Galaxy: A Scientific Revolution
At the end of the 19th century, astronomers were able to identify Andromeda as a spiral structure, disproving the long-held belief that it was simply a "nebula." This revelation marked a paradigm shift: there are many galaxies beyond the Milky Way.
Today, we know that Andromeda and the Milky Way are on a collision course, moving toward each other at 112 km/s. Although this collision will occur in about 3 to 4 billion years, it has already begun at the structural level.
The Galactic Fusion: The Birth of Milcomeda
During the collision, many stars will collide or be affected
by gravity, although direct collisions will be rare due to the vast distances
between stars. The merger will result in the destruction of the current spiral
shapes of both galaxies, creating a new galaxy, likely elliptical or even polar
ring-shaped, nicknamed "Milcomeda."
- Proposed name: Milcómeda (Milky Way + Andromeda)
- Estimated time of complete fusion: 3 billion years after the start of the collision
The Importance of the Andromeda Galactic Halo
Recent research has shown that Andromeda's halo is already
extending toward the Milky Way, spanning about 1.3 million light-years, which
is roughly half the distance between the two galaxies.
This halo is composed of two layers:
- Outer layer: Evenly distributed gas
- Inner layer: More dynamic due to supernova explosions
How do you study an invisible structure?
Since the galactic halo doesn't emit its own light, scientists used ultraviolet light from more than 40 distant quasars, whose radiation is partially absorbed by the Andromeda halo. By analyzing this absorption, they were able to determine the halo's composition and extent.
- Method used: UV observation of quasars from the AMIGA project
- Result: Confirmation of the interaction between galactic halos
And the Triangle Galaxy?
The galactic collision may not be an event exclusive to
Andromeda and the Milky Way. It is suspected that the Triangulum Galaxy, the
second brightest spiral galaxy after Andromeda, could also be part of this
future galactic megamerger.
Conclusion
The James Webb Telescope and other modern scientific tools are allowing astronomers to reveal surprising aspects of our galactic neighbor. The discovery that the collision with Andromeda has already begun at a structural level change our understanding of the cosmic fate of the Milky Way. Although humanity will not directly witness these events, studying them offers us a fascinating glimpse into the future of the universe.