Galaxies King City Astronomy 1 Class 3 Zoe Buck
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Galaxies
King City Astronomy 1Class 3
Zoe Buck
The Most Important Things about Galaxies
• Galaxies are made of gas, dust, and stars, and a lot of dark matter
• Galaxies are gravitationally bound systems that rotate around a center of gravity, typically it the center of the galaxy
• There are many, many billions of galaxies in our Universe
• We see many types of galaxies, and we classify them according to a very simple system that includes elliptical, spirals, barred spirals and irregular
• The Milky way is a barred spiral galaxy• When we look back in time we see very
young galaxies, called quasars, which have very active black holes
• Most galaxies still have super-massive black holes at their centers, and the gravity of these BHs power the rotation of the stars and gas around the center
• Our Milky Way is a barred Spiral Galaxy, which has a disk, a nuclear bulge, a halo, and a galactic nucleus
How Do We Know?
90% of a Spiral Galaxy is Dark Matter!
Galaxies seem to take one of four different appearances
SPIRALS
Galaxies seem to take one of four different appearances
BARRED SPIRALS
Spirals Viewed at Different Angles
Galaxies seem to take one of four different appearances
ELLIPTICALSType E0 Type E3 Type E6
Galaxies seem to take one of four different appearances
IRREGULAR
1 2 3
4 5 6
7 8 9
Looks like a star….but it is 4 billion light years
away!
What are Quasars?
Quasars get their energy from swallowing up matter in the accretion disk
Anatomy of a Spiral Galaxy like the Milky Way
The Most Important Things about Galaxies
• Galaxies are made of gas, dust, and stars, and a lot of dark matter
• Galaxies are gravitationally bound systems that rotate around a center of gravity, typically it the center of the galaxy
• There are many, many billions of galaxies in our Universe
• We see many types of galaxies, and we classify them according to a very simple system that includes elliptical, spirals, barred spirals and irregular
• The Milky way is a barred spiral galaxy• When we look back in time we see very
young galaxies, called quasars, which have very active black holes
• Most galaxies still have super-massive black holes at their centers, and the gravity of these BHs power the rotation of the stars and gas around the center
• Our Milky Way is a barred Spiral Galaxy, which has a disk, a nuclear bulge, a halo, and a galactic nucleus
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