Summerize how galaxies might have formed and grown.
Since this is not my area of expertise, I searched Google under the key words "galaxy formation" to get these possible sources:
http://en.wikipedia.org/wiki/Galaxy_formation_and_evolution
http://abyss.uoregon.edu/~js/ast123/lectures/lec25.html
http://imagine.gsfc.nasa.gov/docs/teachers/galaxies/imagine/page22.html
http://zebu.uoregon.edu/1996/ph123/galaxies.html
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.
I hope this helps. thanks for asking.
Galaxies are vast systems of stars, gas, and dust held together by gravity. The formation and growth of galaxies is a complex and ongoing area of scientific research, but the prevailing theory is that galaxies formed through a process known as hierarchical merging.
Here's a step-by-step explanation of how galaxies might have formed and grown:
1. Initial Density Fluctuations: In the early universe, tiny fluctuations in the density of matter began to emerge. These fluctuations were a result of the random distribution of matter and energy left over from the Big Bang.
2. Gravitational Collapse: Over time, regions with slightly higher than average densities attracted more matter towards them due to the force of gravity. This led to the gravitational collapse of these regions, forming small clumps of matter called protogalactic clouds.
3. Protogalactic Clouds: Protogalactic clouds were composed of gas (mostly hydrogen) and dust. As the clouds continued to collapse under gravity, they began to heat up and spin, forming a rotating disk-like structure.
4. Star Formation: Within the protogalactic clouds, regions of higher density known as stellar nurseries formed. These nurseries were composed of gas and dust, which gradually condensed and ignited to form stars. The stars began to release energy in the form of light and heat.
5. Galaxy Mergers: As the universe continued to evolve, protogalactic clouds started to merge due to their mutual gravitational attraction. These mergers triggered bursts of star formation, leading to the formation of more massive and complex galaxies.
6. Galactic Evolution: Over billions of years, galaxies continued to grow in size through mergers with other galaxies. The more mergers a galaxy experiences, the larger and more massive it becomes. This process, known as hierarchical merging, helped shape the diverse range of galaxies we observe today, from spiral galaxies like the Milky Way to massive elliptical galaxies.
It's important to note that our understanding of galaxy formation and growth is still evolving, and there are various theories and models that scientists continue to explore. Observation of distant galaxies and computer simulations are crucial tools for studying these processes and further unraveling the mysteries of our cosmic neighborhood.