1. The Big Bang Timeline Rapid Expansion of the Universe
2. Atoms of lighter elements such as Hydrogen and
Helium begin to form.
Gravity draws particles of gas and dust together
into gas clouds.
Stars form from the gas clouds.
5. Solar systems form around stars
6. Galaxies form from clusters of stars

2. Galaxy Formation Our Solar System is in the Milky Way Galaxy
Galaxies form from the accretion of star clusters and are
different for different types.
Our Solar System is in the Milky Way Galaxy
2. There are Three types of Galaxies:
Spiral Galaxies (ex. the Milky Way)
B. Elliptical Galaxies
C. Irregular Galaxies

3. Spiral Galaxies Spiral galaxies have a bulge in the center with
spiral arms made of gas, dust, and stars.
The Milky Way Galaxy is a Spiral Galaxy.
Our Solar System is located within a spiral arm of the Milky
Way Galaxy.

4. Elliptical Galaxies Have no spiral arms and are
spherical or egg shaped.
Have very little gas or dust
Spiral Galaxy Elliptical Galaxy

5. Irregular Galaxies
Galaxies that are not spiral or elliptical are irregular, meaning
they have no particular shape.