Recap Galaxies

1
Recap Galaxies

• Describe similarities and differences in the
  observation of a galaxy and of Crab Nebula
• Describe our galaxy (the Milky Way)
• What type of observation was most important in
  establishing the type of our galaxy ?
• What types of galaxies are in the Universe and
  which type is most abundant ? Is there a link
  between various type of galaxies ?
• Discuss the types of active galaxies and the
  possible link between these types.

2
The Creation of the Universe

• The Universal Expansion
• Big Bang or Continuous Creation ?
• The Temperature of the Universe
• The First Fractions of a Second
• Where is the Anti-matter ?
• After the First Second

3
The Universal Expansion

• Cosmogony the early biography of the Universe
  (the archeology of the Universe)
• V.Slipher (1912) and E.Hubble(1923) showed the
  most galaxies have the atomic spectra shifted
  towards red.
• 1929 - Hubble and Humason established that this
  shift increases with the galaxies becoming dimmer
  and dimmer. Hubble plotted galaxies speed vs
  distance and that plot bears his name. Galactic
  distances were calculated with Cepheid stars
  measurements.

4
Big Bang or Continuous Creation ?

• 1922 - A.Friedman showed that Einsteins general
  relativity equations can have a solution
  corresponding to an expanding or contracting
  Universe.
• 1926 - Hubbles diagram showed that all galaxies
  started from the same point. Unfortunately,
  Hubble obtained a life of the Universe shorter
  than the age of Earth (as found in the studies of
  rocks and fossils)
• H.Bondi, T.Gold and F.Hoyle proposed a Continuous
  Creation (or a Stationary State) model of the
  Universe, which uses intergalactic white holes.
• 1952 - W.Baade at Palomar discovers the error in
  Hubbles observations and makes the Universe
  older than Earth.
• 1951 - the Vatican officially supports the Big
  Bang model.
• 1950s - G.Gamow, R.Alpher and R.Hermann determine
  the production of elements during the first
  moments of the Big Bang.
• Hoyles model continued to be a direct
  competitor of Big Bang. But in 1965 another
  discovery eliminated completely Hoyles Continuum
  Creation.

5
The Temperature of the Universe

• In 1965 Bell Labs announced that the Universe
  contains a radio energy corresponding to a
  temperature of 3 Kelvin degrees (or 270 degrees
  Celsius). That agreed well with the Big Bang
  model.
• Accidents at Bell Labs
• 1931 K.Jansky did the first radio-astronomical
  observations
• 1965 A.Penzias and R.Wilson discovered the cosmic
  microwave radiation.
• R.Dicke at Princeton was able to repeat the
  experiment of Penzias and Wilson and that marked
  the publication of the result known to physicists
  as the Universal 3oK black body radiation.

6
The First Fraction of a Second (I)

• Big Bang was the most powerful phenomenon
  imaginable.
• At less than 10-35 seconds from the beginning of
  the Big Bang and at temperatures above 1028
  degrees the 10-dimensional Universe had a
  democracy of particles (squeezed at distances
  smaller than 10-33 cm) and forces.
• At a slightly lower temperature a symmetry
  breaking created an abundance of super-heavy
  Higgs bosons, which gave the weight (1015 GeV) to
  the hyper-weak force carriers. The hyper-weak
  force transformed baryons into leptons and
  anti-baryons into anti-leptons.

7
The First Fraction of a Second (II)

• The asymmetry in the hyperweak transformations
  makes the disintegration of anti-baryons more
  probable. This created a Universe dominated by
  particles over anti-particles. More exactly it
  created the observed ratio of 1 anti-hadron to
  10,000 hadrons.
• It also created the observed ratio of 1 baryon to
  1 billion photons.
• How to measure these ratios ? One can weigh a
  galaxy from its dynamics and one can measure its
  size. The result is an average density of about
  10-6 10-8 baryons per cubic cm. The density of
  photons is found by physicists to be about 400
  photons per cubic cm.
• It is remarkable that the same ratio of
  baryons/photons is obtained from a model of Big
  Bang at temperatures above 1012 degrees.
• This period has a huge predominance of radiation
  (photons at energies of MeV) over matter (baryons
  at energies of GeV) . Today while the ratio is
  preserved, the photons have energies of order of
  10-3 eV and that change makes matter more
  important than radiation.

8
The First Fraction of a Second (III)

• After 10-4 seconds from beginning of the Big Bang
  the Universe reached a temperature of 1012
  degrees.
• In this state theorists believe that small
  fluctuations were amplified and lead to the
  formation of galaxies.
• Recent calculations show that a model with 6
  types of quarks leads to a soup of hadrons
  capable to produce galaxies.
• Between 10-4 and 10-3 seconds at a temperature of
  1011 degrees most heavy baryons disintegrated
  creating protons and neutrons and a large number
  of neutrinos, while the radiation created pairs
  of electrons and positrons.
• At about 10-3 seconds from the beginning of the
  Big Bang, after the breaking of symmetry
  occurring when particles were at distances of
  around 10-16 cm, the fundamental forces were
  functioning like today.

9
The Inflationary Model (I)
The Grand Unified Theories - based Inflationary
Model predicts a 50 orders of magnitude increase
for the 10-32 seconds old Universe.
1
10-10
size (cm)
10-50
10-60
10-35
10-25
10-15
time (sec)
10
The Inflationary Model (II)

• How is the inflation possible ?
• Vacuum is a bubbling environment based on
  quantum fluctuations of mass-energy. Guth has
  shown that it is possible to buildup these
  quantum kicks to create galactic seeds. In
  some very few places inflation yields to the
  creation of a new Universe.
• Guth showed that for the Universe to be the way
  it is the inflation doubling its size 100,000
  times should have stopped after 10-30 seconds
  (the inflation energy had to decay).

11
After the First Second (I)

• S.Weinberg The First Three Minutes
• At 10 billion degrees the neutrinos decoupled
  from the rest of particles and the weak force
  stopped from changing protons and neutrons their
  ratio froze to a value 1/6-1/7.
• At 3 billion degrees the radiation was unable to
  create pairs of electrons/positrons and the
  density of photons became a constant (like that
  of neutrinos)
• At 1 billion degrees the fusion of protons
  started. It formed deuterons and then helium
  nuclei. In only 200 seconds this process changed
  about a quarter of protons into helium nuclei.
  Todays observed ratio of helium to hydrogen is
  3/10, with the extra 5 increase being due to the
  fusion reactions inside the stars.
• The total number of baryons observed today in
  stars and intergalactic is related to the number
  of particles which were produced during the Big
  Bang and this link established that the number of
  quarks can be either 6 or maximum 8.

12
After the First Second (II)

• The cooling of the Universe happened in a few
  hundreds of thousands of years.
• At 5000 degrees (the temperature at the surface
  of our Sun), the radiation was separated from
  heavy matter and the cooling continued separately
  for the heavy matter, for photons and for
  neutrinos.
• The cooling of the photons lead in time to the
  microwave radiation observed by Penzias and
  Wilson. Zeldovich and his collaborators
  determined that the temperature of the neutrinos
  should be today around 2 absolute degrees (still
  undetectable)
• The first atoms were formed about 300,000 years
  from the beginning of the Big Bang, when the
  Universe was about 20,000 smaller than today.

13
Galaxies Formation

• The first galaxies were formed when the Universe
  was about 100 million years old having a density
  about 10,000 larger than today.
• A possible scenario considers primordial black
  holes as the seeds for their formation (it is
  also possible that simple clouds of matter
  separated during the expansion).
• Young galaxies are associated with quasars and
  the fact that the most remote quasars correspond
  to an age of the Universe of about 1 billion
  years indicates that the galaxies before that
  time were too small or dim to be seen today.
• The first stars inside galaxies were probably
  formed in parallel to their activity as quasars.
  Our solar system corresponds to 2nd or 3rd
  generation of stars which use a large
  concentration of heavy elements produced in
  supernovas.
• The separation of galaxies of different sizes
  would create a non-uniform Universe, in
  contradiction with the current galactic
  observations. A.Guth inflationary model provides
  the explanation for a uniform distribution of the
  clusters of galaxies.