How did galaxies form and evolve into the galaxies we know today?

The question of how galaxies formed is one of the most important questions in observational cosmology. We would all like to know what is actually correct, but there are still many puzzle pieces to be filled in.

The rationale, which everyone agrees on, is that gravity drives the formation of galaxies. Where the consensus is also quite broad, but not general, is that the ‘ordinary’ matter, consisting of protons and neutrons and electrons, is not sufficient to give rise to galaxies in the universe quite quickly, and that there are therefore ‘ dark matter is needed.

It is also becoming increasingly clear that galaxies have grown more or less gradually through the merging of smaller systems. We see that in the past universe there were more but smaller galaxies, and also in our own galaxy today we see indications that galaxies have been absorbed by ours quite recently. How those individual histories ultimately explain the diverse forms of galaxies today has not been fully explored.

A big question is what role the supermassive black holes at the centers of many galaxies play in the story. Did they grow from the collisions of galaxies, or were they, on the contrary, the seeds around which galaxies formed? A wide range of questions has to do with the role of star formation in the formation of galaxies. Indeed, there is a complex feedback here. It is where matter comes together that stars are formed, but on the other hand, the radiation from stars drives matter apart.

It’s no wonder we don’t know it all yet. Most galaxies formed a long time ago, and we have to look deep into the universe to see that happen. The large telescopes that make this possible have only been around for a good ten years, and they live up to expectations. The ESA satellite Herschel has also been operational for three years now, and it allows us to study the dominant infrared radiation of young galaxies. And now the large (sub) mm telescope Alma is also coming into use, and the first results are nothing short of fascinating. In ten years’ time, we will have super-sized optical telescopes.

As a 17-year-old, you shouldn’t be disappointed that there is still so much we don’t know, but rather happy that there is still so much to discover. I myself am 57, and every day I am fascinated by the richness of the phenomena that we are allowed to discover.