A Brief, Abbreviated Review Synopsis of Subjects Covered in
Astro 150
Part III: Galaxies, Cosmology, and Life
- The Milky Way
- the interstellar medium
- basic dimensions and structure: ping-pong ball in CD,
100,000 light years across
- rotation: fast rotation in outer parts indicates there must
be a dark massive halo
- spiral arms - spiral density wave
- the Milky Way neighborhood - nearby galaxies like Andromeda,
Magell. clouds
- Galaxy Types: spirals; barred spirals: ellipticals; interactions
- Galaxy Distances - the distance pyramid; more reliable close
by, less reliable farther away
- Cepheid variable stars: period-luminosity relation
- internal velocity dispersion correlation to luminosity
(Tully-Fisher)
- Type Ia Supernovae, average galaxy characteristics
- The Hubble Law
- velocity of recession (through Doppler) proportional to
distance
- the Hubble constant: H, in range from 50 to 100 km/s per
million parsecs - best current value is 70 +/- a few
- the expanding universe: all galaxies move away from each
other
- no center for expansion, not an explosion
- Freaky Galaxies
- Quasars - point-like objects with huge red Doppler shifts -
large distances
- rapidly varying brightness - small
- high luminosity
- huge structures visible at radio wavelengths
- Active galaxies (Seyferts, BL Lac objects, radio galaxies)
- supermassive black hole as energy source
- Clusters and superclusters
- galaxies cluster on the megaparsec scale
- clusters also show larger scale organization: the great
wall
- Cosmology - a big, expanding, and structured universe
- age = 10 to 20 billion years (best guess: 13 billion)
- expansion now implies a Big Bang in past
- Big Bang - produced H, He, and lithium from initial pure
energy fireball
- tests - pervasive 3 K background radiation - observed by
COBE
- problems: uniformity over all space - how to form structure
of supercluster scales?
- seeds of galaxy formation discovered by COBE, explored by WMAP and PLANCK
- Open vs. Closed universe: the critical density; tests;
current guess is flat (Omega = 1)
- dark matter can't be ordinary atoms - must be 'non-baryonic'
- inflation - rapid early expansion leaving us with density
equal to critical density
- the accelerating universe - Type Ia supernova results
- the Cosmic Web
- if closed, recycled universe (bang, expand, contract,
crunch, bang, expand, ...
- Search for Extraterrestrial Intelligence
- The Drake Equation: probability of other civilizations in
space
- Extrasolar planetary systems
- communicating with ET