Galaxies become more chaotic as they age

Image: NASA

Until now, astronomers do not know exactly why this happens, as the reason has been searched for in the galaxy's environment or its mass. But new research shows that neither is the most important factor: the tendency for stars to move randomly is mainly due to the age of the galaxy. As time goes by, the galaxy simply becomes more chaotic.

“When we conducted our analysis, we found that age was always the most important factor,” said lead author Scott Crum, a professor at the University of Sydney (Australia). If you take into account the age of the galaxy, there will be no environmental trend, and the same applies to mass: if you are dealing with a young galaxy, it will rotate no matter what environment it is in. If it were an old galaxy, the orbits of the stars would be more random, regardless of whether the galaxy was in a crowded or empty environment.

Thick tablet

The new research is based on studies in which environment or mass were considered the most important factors. This earlier work is not necessarily incorrect, according to second author Jesse van de Sande. “We know that the age of a galaxy is affected by its environment. If a galaxy reaches a densely populated environment, star formation will stop. As a result, galaxies in a crowded environment are older on average. The point of our analysis is that remaining in a dense environment does not reduce their rotation; But the fact that they are older.

Our galaxy, the Milky Way, has a thin star-forming disk and is therefore still considered a rapidly rotating galaxy. But if you look closely at the Milky Way, you'll see something called a thick disk. In terms of light, it's not dominant, but it's there. This thick disk appears to be composed of older stars that may have formed in the young, more turbulent universe.