What is a Galaxy?
It is a group of billions
and billions of stars
held together by gravity.
Universe
All existing
matter;
everything
Spiral Galaxy
Bulge
Disk
Top View
Side View
•Huge; contains stars, gas, and dust
•Held together by gravity
•Pinwheel shape/looks like a hurricane
•Bulge and thin disk
•Halo (glow) is present
•Rich in gas and dust
•Young and old stars are present
The
“Milky Way”
galaxy is a
spiral galaxy.
The Sun is in a
spiral arm halfway out from
the center.
Map of Milky Way
Our Sun(yellow dot) is in a spiral arm, ½-way out
Spiral Galaxy
Spiral Galaxy
Spiral Galaxy
Spiral Galaxy
Elliptical Galaxy
•Huge; contains stars, gas, and dust
•Held together by gravity
•Round to oval
•Bulge but no disk
•Halo is present
•Little cool gas and dust
•Mainly OLD STARS are present
Elliptical Galaxy
Elliptical Galaxy
Elliptical Galaxy
Elliptical Galaxy
Irregular Galaxy
•Huge; contains stars, gas, and dust
•Held together by gravity
•No regular shape
•May show signs of a disk and/or bulge
•Halo is present
•Usually rich in gas and dust
•Young and old stars are present
Irregular Galaxy
Irregular Galaxy
Irregular Galaxy
Nebulae
Planetary Nebula
(death of a star)
Movie
Stellar Nebula
(where stars are born)
Stellar Nebula
Stellar Nebula
Stellar Nebula
Stellar Nebula
Planetary Nebula
Planetary Nebula
Planetary Nebula
Planetary Nebula
Colliding Galaxies
Betelgeuse
Rigel
Orion Constellation
Supernovae
Sun/main
sequence
star
Stellar
Nebula
Stars form in a
nebula from
collapsing
clouds of
interstellar
gas and dust.
Red
Giant
Planetary
Nebula
Protosta
r
Massive
Star
Neutron
Star
Red
Supergiant
Supernova
Black
Hole
White
Dwarf