Have new galaxies formed?

[weeman]

<p>From all the sources I've seen (including this forum) about the total number of galaxies in the observable universe, the average seems to hang right in the range of 200-400 billion galaxies. So, we can conclude that the average number of stars with that amount of galaxies is roughly 70 sextillion. Giving us <em>astronomical </em>chances for other life-bearing planetary systems. </p><p>However, since the light of many of these galaxies has taken several billion years to reach us, how many new galaxies have formed in the universe in that time? Is it possible that our universe is even more populated with new galaxies who's light has yet to reach us? Is it possible that the estimated number of 200-400 billion could have easily doubled within the last 12.7 billion years? </p><p>Thanks <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-laughing.gif" border="0" alt="Laughing" title="Laughing" /></p> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[Carrickagh]

<p>That's a very good question and one that astronomers are still grappling with. Observations from the Hubble Space Telescope favor an idea that galaxies formed via the merging of gas clouds. There is one famous image (not as famous as the Deep Field) that shows all these tiny splotchy sub-galaxies in&nbsp;a cluster. I beleive it was taken in the Hercules constellation. The objects in this image are about 11 billion ly away. These little shrimp galaxies are much smaller than even the small-scale galaxies in the "present-day" and have irregular shapes. Also, in these HST images the objects are only scattered across about 2 million lightyears, about the distance between Milky Way and M31. It is thought that the objects in this field would collide together and merge into larger galaxies. These collisions would be aided by the dark matter associated with these small, sub-galaxies. The dark matter would increase the object's mass and thus the gravitational forces pulling these objects together. Such mergers of these little guys would eventually yield a "normal-sized" galaxy.</p><p>So, based on this idea perhaps there are actually fewer galaxies now, via this process of mergers.</p><p>Galactic evolution is both a controversial and difficult subject. There are many unresolved questions. For instance, where did the sub-galactic clumps of gas come from? And what happened in the early universe to cause the ancient hydrogen and helium to clump up into objects destined to evolve into galaxies? Why didn't they form objects a zillion times bigger or smaller? And of course the more troublesome issue is dark matter, which constitutes 90% of the mass in our and other Galaxies.</p><p>CK</p> <div class="Discussion_UserSignature"> </div>