Week 8 Galaxies Flashcards
when does a nebula collapse
when the radius is > Jeans radius or the mass is greater than the Jeans mass
what is the Jeans radius equation
Rj = sqrt[ 15/4π kT/Gmρ ]
what is the Jeans mass equation
Mj = sqrt[ 3/4πρ ] (5kT/Gm)^3/2
what happens once a cloud of gas begins to collapse
it becomes unstable on progressively smaller scales known as fragmentation
what are the 4 types of galaxies
Elliptical
Spiral
Barred Spiral
Irregular
give the 4 properties of Elliptical galaxies
Ellipsoidal
Little internal structure
Red colours from low mass stars
No star formation
give the 3 properties of a spiral galaxy
central bulge
rotating disk surrounds bulge
star formation can take place
how do barred spiral galaxies differ to regular spiral galaxies
have a central bar rather than a bulge
what are the 2 properties of an irregular galaxy
diverse structures
allow star formation
what determines whether two galaxies collide
mean free path
what is the collision cross section area equation
σ = πd^2
d is the diameter of the galaxy
what is the mean free path equation
λ = 1 / nσ vt(collision)
n is the number density
λ is the length travelled
what is the general rule for time between collisions
the time between collisions is ~ 10 times the age of the galaxy
what can be said of collision between galaxies
large collisions happen very rarely however minor collisions between small galaxies and large galaxies happen frequently.
what is at the centre of most galaxies
supermassive blackhole
