Cosmology Flashcards
Define the Doppler effect
An increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move towards (or away from) each other
Give the equation for the Doppler shift of the light from the atoms of a star with an original wavelength of λ and velocity v
z = Δf / f = v /c and Δλ / λ = - v / c
This applies when v
Give 2 applications of the Doppler effect
1) Calculating the recession of galaxies from the amount of redshift
2) Determining the rotational velocity and thus distance between eclipsing binary stars
Define eclipsing binary stars
Binary systems that orbit in the same plane as the line of sight of Earth
State Hubble’s law
The recession velocity is proportional to the distance from the Earth
v = H₀d
where H₀ is Hubble’s constant (60-80kms⁻¹Mpc⁻¹)
Give the units for Hubble’s constant
kms⁻¹Mpc⁻¹
Define the Hubble period and state an assumption
t = 1 / H₀
This gives the approximate age of the universe assuming the rate of expansion of the universe has been constant (which it hasn’t)
State what is thought to be the cause of the acceleration of the expansion of the universe
Dark energy, which provides a repulsive force that opposes the gravitational force in the universe
State the order of the stages for the expansion and evolution of the universe from the big bang theory
1) Big Bang
2) Cosmic Inflation
3) Particles Form
4) Recombination
5) Dark Ages
6) First Stars and Galaxies
7) Galaxy Evolution
Give 2 key pieces of evidence for the big bang theory
1) CMBR (Cosmic Microwave Background Radiation)
2) The abundance of Helium
Give 2 types of Quasars
QSOs (Quasi-stellar objects)
QSRs (Quasi Stellar Radio Sources)
Define Quasars
A massive and extremely remote celestial object, emitting exceptionally large amounts of energy, which typically has a starlike image in a telescope and have a variability that is irregular
What suggests that quasars are extremely distant objects?
They have huge red shifts, showing them to be receding at 14-95% of the speed of light, therefore meaning they are extremely large distances from the Earth.
They are the most distant objects we can see
Describe Quasars in terms of their black hole properties
Quasars exhibit properties of very active galaxies that are powered by supermassive black holes (which typically consume 10 stars per year). The brightest quasars are thought to consume up to 1000Ms per year; a rate of consumption that is not sustainable for a long period of time, hense the quasars can turn on and off.
What happens to a quasar once it finishes consuming all that it can?
The remaining matter becomes an ordinary galaxy
