Lecture 35 Flashcards
What are bright spots in the CMB?
Seeds of galaxy clusters and large-scale structure
What are the origins of density/temperature fluctuations in the universe?
- occurred in the Planck Era
- quantum fluctuations expand with the universe
- uncertainty principle- cannot tell exact position (or energy) on the Planck scale
What are peaks and valleys in the CMB?
- quantum fluctuations before inflation lead to slight differences in matter distribution
- matter was pulled into the valleys and denser regions attract particles from less dense regions by gravity
What can we think of CMB temperature anisotropies as?
The seeds of structure
What is the density contrast?
- denser regions have more gravity than less dense regions
- matter is pulled into dense regions from less dense regions
How is the cosmic web formed?
- gravity makes dense regions get denser and empty regions get emptier
- the cosmic web is formed with galaxies at the centre of collapsing halos
What is the largest redshift that we can make observations to?
Around z~10 but it is very difficult
What occurred during the Dark Ages (~400,000yr to ~50Myr)?
- the universe was made of neutral hydrogen
- cooling
- density was too small to form galaxies and stars
What occurred during the Epoch of reionisation?
- around 50 Myrs after the big bang
- first light appears
- hydrogen reionisation begins
What occurred at around z~50-10?
- regular matter collapses into the centre of dark matter halos (cold enough to reach high density)
- first stars formed
- cores of protogalaxies may host large black holes (quasars)
- first starlight is redshifted to mid-IR
When approximately did the first galaxies form?
z~ 15-8
What occurred during the ionised universe?
- t~600 Myr
- enough stars and galaxies to keep hydrogen ionised
- universe becomes transparent to UV
What occurred during the era of galaxies?
-z= 8-1
- large galaxies (Milky Way) formed
- star formation was at its maximum
- many galaxy collisions
What occurred during the modern universe?
- z<1
- fewer stars form
- most galaxies in a stable form
- the solar system forms (z=0.6)
What does the future of expansion depend on?
How dark energy behaves
What are the three theories for the future of the universe?
- big rip
- constant dark energy
- big crunch
What would occur in a heat death?
- constant dark energy accelerates the universe
- Hubble constant grows
- everything redshifted into oblivion
- everything stops- the big chill
What will happen to the Milky Way?
In ~2-4 Gyr it will collide with Andromeda and become an elliptical galaxy
What will happen to the Sun ~5 Gyr?
It will become a red giant, planetary nebula then white dwarf
What will happen at ~100 Gyr?
Expansion accelerated so fast that all galaxies are beyond our horizon and only red dwarves remain
What will occur at ~10^12 years
All stars will have reached the end of their lives. Proton decay may occur
What will happen at ~10^37 years?
Only black holes will remain- they will be evaporating
What will occur at ~10^100 years?
Black holes are gone. Only electrons,
neutrinos, proton decay products,
and photons exist. The temperature will be 0K.
