How are galaxies formed?

Astronomers Uncover A Surprising Trend in Galaxy Evolution

Milky Way

How was the Milky Way formed?

A surprising pattern of galactic evolution emerged in recent study by NASA astronomers. Contrary to their opinion that nearby galaxies had achieved their present state 8 billion years ago, observations suggest galaxies were changing steadily during this time period. They found that the most distant blue galaxies exhibit disorganized motions in multiple directions, much different from disk-shaped galaxies where rotation dominates over other internal motions, such as the Andromeda Galaxy or the Milky Way. Gradually, disorganized motions dissipate and rotation speeds increase, whereby galaxies settle into organized disks.

In the past 8 billion years, the number of mergers between galaxies large and small has decreased sharply. So has the overall rate of star formation and disruptions of supernova explosions associated with star formation. Scientists speculate these factors may play a role in creating the evolutionary trend they observe. Now after finding see this pattern, astronomers can adjust computer simulations of galaxy evolution until these models are able to replicate the observed trend. This will guide scientists to the physical processes most responsible for it.