How far back can we look to search for evidence of newborn galaxies?
The nearby Universe is filled with several kinds of galaxies.
These are galaxies like the Milky Way that consist of a central bulge (or nucleus), a spherical stellar component (older), and a flattened disk.
The disk contains stars and gas, and the gas component is often concentrated in large spiral arms where we find the youngest stars (dominated by massive and short-lived blue stars).
The outer spherical component consists of old stars (red) that probably formed early in the life of the galaxy (includes the globular star clusters).
The central bulge contains many old stars and sometimes a supermassive black hole. We often find a linear structure associated with the bulge: such galaxies are called BARRED SPIRALS.
Many spiral galaxies rotate in a way which indicates the presence of a massive halo of dark matter.
These contain old stars but no gas.
These contain stars and gas but in no obvious form.