Galaxies, part 1: Crash Course Astronomy #38

What was the main debate between Harlow Shapley and Heber Curtis in 1920?

• Whether the Milky Way was the entire universe or one of many galaxies

• Whether the Sun was at the center of the universe

• Whether stars were made of gas or solid matter

• Whether the Earth was flat or round

What discovery did Edwin Hubble and Milton Humason make about the Andromeda Nebula?

• It was a part of the Milky Way

• It was a black hole

• It was a separate galaxy outside the Milky Way

• It was a cluster of stars within our solar system

What are Cepheid variables?

• Planets that orbit around stars

• Stars that change their brightness in a regular, periodic fashion

• Galaxies that collide with each other

• Nebulae that emit radio waves

What is a characteristic feature of spiral galaxies?

• They are formed from galactic collisions

• They are nearly spherical and lack structure

• They have a broad, flat rotating disk of stars, gas, and dust

• They are composed entirely of dark matter

What is the main characteristic of elliptical galaxies?

• They have a lack of gas and dust and are populated with older stars

• They have well-organized spiral arms

• They are primarily composed of young, blue stars

• They have a central bulge with a bar of stars

What happens during a galactic collision?

• Galaxies merge instantly

• Gas clouds collide and form new stars

• Galaxies shrink in size

• Stars physically collide with each other

What is the result of a galactic collision?

• Formation of a new solar system

• Creation of a black hole

• Destruction of all stars involved

• Formation of elliptical galaxies

What is the process by which large galaxies grow by consuming smaller ones?

• Galactic cannibalism

• Star formation

• Black hole absorption

• Nebula expansion

What are the four major types of galaxies?

• Large, medium, small, and tiny

• Bright, dim, colorful, and monochrome

• Circular, oval, rectangular, and triangular

• Elliptical, spiral, peculiar, and irregular

What is the significance of the discovery of Cepheid variables in the Andromeda Galaxy?

• It proved that galaxies do not exist

• It indicated the presence of a black hole

• It showed that the galaxy was part of the Milky Way

• It helped determine the distance to the galaxy, proving it was outside the Milky Way