Universe & the Galaxies

Allow me with this introductory slide :) Where or what are we in the whole scheme of things?

This is Milky Way - our Home galaxy. 13+ billion years old! It's a huge barred spiral galaxy (as seen on right pix); with ~100,000 light years in diameter and 1000 light years in width. It has 200-400 billion stars (our Sun is just 1 of them), and countless planets.

The picture on the left hand side is an actual picture of our galaxy, as seen from Earth. This is sometimes visible in a lightless, moonless night - i think better viewed in the southern hemisphere. I recall from History channel, that during Einstein's time - they thought that THIS IS the universe. Over time, somebody realized that one of the bright shining stars in the picture - is actually another giant galaxy - Andromeda! Our twin galaxy sister, which by the way is approaching us, and is expected to collide with Milky in 3-4 billion yrs time.

Now to put things in perspective; Milky Way and Adromeda are part of a 50-galaxy group (small ones include Magellanic cloud- galaxies which are visible from Earth), which in turn is part of an even larger Virgo Super-cluster, which is just one of the billions of millions of galaxy clusters in the universe.