AST201 Lecture 6 Notes.docx

3 Pages
Unlock Document

University of Toronto St. George
Astronomy & Astrophysics
Stephen Reid

Lecture 6 – February 5 Reading: 5.3 1. Disk Population: A group of stars that orbit the galactic center, in a disk shape. (flat) (consists of stars made after the gas in the protogalactic cloud settled into a rotating disk) 2. Protogalactic Cloud: When clouds were formed in the early universe ( 70% hydrogen, 30% Helium) These clouds form galaxies. REMEMBER THIS: Gas back in time was equally distributed, but than that gas started to move in the most dense areas, which than became a center- (the gas is called Protogalactic cloud) The center is what you call a galaxy. 3. Spheroidal Population: A more random design of orbiting. (random oriented orbits) (Consists of stars that were brown before it’s galaxies rotation) 4. WHY ARE GALAXIES DIFFERENT? There are 2 hypothesis for this condition: a) The galaxies differ because their protogalactic clouds had slightly different conditions. b) Galaxies may have started similarly to the other galaxies, but later changed because they interacted with other galaxies. 5. SPIRAL GALAXIES HAVE GAS-RICH DISKS , ELLIPTICAL GALAXIES DO NOT:Why ? Either because of a Protogalactic spin , or the Protogalactic Density. 6. What is a Protogalactic Spin, and Protogalactic Density? Protogalactic Spin: Well it is basically Protogalactic spin is when the angular momentum, defines the type of orbit it will be, Elliptical/ Spiral. Etc. For example, if the cloud has a certain number of angular momentum it would rotate quickly than collapse, this would result into a spiral . If the protogalactic cloud had little or no angular momentum, than it would result in having no disk, thus resulting in a elliptical galaxy. Protogalactic Density: High gas density- radiates more energy than low gas density . (opposite) IMPORTA
More Less

Related notes for AST201H1

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.