Editing Galactic Structure (section)

== <span style="color: #FFFFFF;">Understanding</span> ==
Galaxies are structured like '''Rotating Cities''' with distinct zones.

'''1. The Types of Galaxies (The Hubble Tuning Fork)''':
* '''Spirals''' (like the Milky Way): "Factories" of new stars. The blue spiral arms are where new, hot stars are being born from gas and dust.
* '''Ellipticals''': "Retirement homes." They have used up all their gas, so no new stars are being born. They contain only old, red stars.
* '''Lenticular''': A hybrid with a disk but no spiral arms.

'''2. The Milky Way's Anatomy''':
* '''The Nucleus''': At the very center (Sagittarius A*) sits a Supermassive Black Hole.
* '''The Disk''': This is where we live. It rotates at 500,000 mph.
* '''The Halo''': Contains the "fossils" of the galaxy—the oldest stars that formed when the galaxy was just a cloud.

'''3. The Dark Matter Mystery''':
When astronomers measure how fast a galaxy rotates, they find it's moving too fast. Based on the visible stars, the galaxy should fly apart like a broken merry-go-round. This proves there is a massive amount of invisible "Dark Matter" providing the extra gravity needed to hold everything together.
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