Class Notes (834,353)
Canada (508,492)
Astronomy (177)
AST201H5 (68)
J B Lester (13)


2 Pages
Unlock Document

J B Lester

AST 201S - Stars and Galaxies University of Toronto Mississauga Chapter 12 Summary th Essential Cosmic Evolution, 5 Edition 1. Star birth - continuing today • There are very massive (thousands of M sun), very cold (10 - 30 K) clouds of interstellar gas/dust • Clouds contract and fragment into star-size masses (0.1 - 100 M sun • Fragmentation produces a few large masses, numerous medium masses and huge numbers of low masses • Gas heats from released stored gravitational energy • Gas becomes opaque, trapping the heat → protostar • Core gets hot enough for fusion to begin • Masses > 100 M sun create too much energy → disintegrate • Masses < 0.1 M suncannot create the conditions for fusion • Stars > 8 M sun - “high-mass” stars, and star < 8 M sun- “low-mass” stars live out their lives in significantly different ways • Star birth is violent as the star sheds angular momentum → jets and powerful stellar winds • About 50% of protostars split into double stars to share the angular momentum 2. Life of a low-mass star (the vast majority of stars) • Create energy by fusion of 4( H) → He - same as the Sun • Rate of fusion decreases going from the centre of the core to the boundary of the core because of decreasing pressure and temperature • Energy leaves the core as radiation • When the centre of the core has converted all of its H to He, the outer core still has plenty of H remaining → gradual adjustment • Centre pressure < gravity → shrinks gradually • Surface gradually expands → becomes red giant star 4 12 • Centre conditions become extreme enough to fuse 3( He) → C • Core expands, surface shrinks → “horizontal branch” star continued on page 2 AST201H5S – Chapter 12 Summary
More Less

Related notes for AST201H5

Log In


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.