Galaxies Flashcards
1
Q
What is a galaxy?
A
A gravitationally bound collection of stars, dust, gas, planets etc
2
Q
What are the three main types of galaxies?
A
Spiral
Elliptical
Irregular
3
Q
What is a spiral galaxy?
A
Consisting of a flat, rotating disk of stars etc. Spiral arms are sites of ongoing star formation and the galaxy contains a bulge of stars
4
Q
What is an elliptical galaxy?
A
Ellipsoidal in shape and smooth and featureless. Comprised of older low mass stars and typically very large
5
Q
What is an irregular galaxy?
A
Often very small and sometimes distorted by nearby galaxies. Make up a quarter of all galaxies
6
Q
What is the mass interior to the orbit of a galaxy?
A
M=RV^2/G
7
Q
What can be noted about orbital velocities of galaxies?
A
They appear constant up until the limit of observations
