Download Chapter 18 - AstroStop

Chapter 18:
Cosmology
WHAT DO YOU THINK?
What does the universe encompass?
 Is the universe expanding, fixed in size,
or contracting?
 Will the universe last forever?
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You will discover…
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cosmology, which seeks to explain how the
universe began, how it evolves, and its fate
the best theory we have for the evolution of the
universe—the Big Bang
how astronomers trace the emergence of matter
and the formation of galaxies
how astronomers explain the overall structure of
the universe
our understanding of the fate of the universe
Cosmological Redshift
Expanding Cake Analogy
Just as all the chocolate chips move apart as the cake
rises, all the superclusters of galaxies recede from
each other as the universe expands.
Bell Labs Horn Antenna
Arno Penzias (right) and Robert Wilson
In Search of Primordial Photons
Wilkinson Microwave Anisotropy Probe
(WMAP) satellite, launched in 2001
In Search of Primordial Photons
The balloon-carried telescope BOOMERANG
Spectrum of the Cosmic
Microwave Background
The Microwave Sky
The Doppler shift across the sky is caused
by the Earth’s motion through the
microwave background.
Our Motion Through the
Microwave Background
Because of the Doppler effect, we detect shorter
wavelengths in the microwave background and
a higher temperature of radiation in that part of
the sky toward which we are moving.
Unification of the Four Forces
Early History of the Universe
The Cause of Inflation
Observable Universe Before
and After Inflation
Pair Production and Annihilation
Evolution of Density
Era of Recombination
Observable Universe
The cosmic light horizon today is about 13.8 billion
light-years away in all directions. Inset: This HST
Deep Field Telescope image shows some of the
most distant galaxies we have seen.
Structure of the Early Universe
This Wilkinson Microwave Anisotropy Probe (WMAP) image shows
temperature variations in the cosmic microwave background. Inset:
Tiny temperature fluctuations, observed by BOOMERANG, are
related to the large-scale structure of the universe today, indicating
where superclusters and voids grew.
Galaxies Forming by Combining
Smaller Units
This painting indicates how
astronomers visualize the burst of star
formation that occurred within a few
hundred million years after the Big
Bang.
Galaxies Forming by Combining
Smaller Units
Hubble and Keck telescope images of two
groups of stars that are believed to be
protogalaxies, from which bigger galaxies grew
Galaxies Forming by Combining
Smaller Units
This Chandra X-ray telescope image shows gravitationally
bound gas around the distant galaxy 3C 294. The X-ray
emission from this gas is the signature of an extremely
massive cluster of galaxies.
Stellar Birth Rates
Star formation continued actively for billions
of years when the universe was very young.
Stellar Birth Rates
Most of the stars in an elliptical galaxy are created in a brief
burst of star formation when the galaxy is very young. In spiral
galaxies, stars form at a more leisurely pace that extends over
billions of years.
Creation of Spiral and
Elliptical Galaxies
A galaxy begins as a huge cloud of primordial
gas that collapses gravitationally.
A Cosmic Timeline
Possible Geometries of the
Universe
The curvature is either
(a) Positive
(b) Zero
(c) negative
Cosmic Microwave Background
and the Curvature of Space
Dimmer Distant Supernova
•These HST images show
the galaxy in which the
supernova SN 1997ff
occurred.
•This supernova was dimmer
than expected.
•The distance to it is greater
than it would be if the
universe had been
continually slowing down.
•An outward force is acting
over vast distances in the
universe.
Dimmer Distant Supernova
WHAT DID YOU THINK?
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What is the universe?
It is all the matter, energy, and spacetime that
will ever be detectable from the Earth or that will
ever affect us.
Did the universe have a beginning?
Yes, it occurred about 13.8 billion years ago in
an event called the Big Bang.
Will the universe last forever?
Current observations support the belief that the
universe will last forever.
Key Terms
Big Bang
closed universe
confinement
cosmic light horizon
cosmic microwave
background
cosmological constant
cosmological redshift
cosmology
dark ages
dark energy
decoupling
era of recombination
expanding universe
grand unified theory (GUT)
homogeneity
horizon problem
inflation
inflationary epoch
isotropy
isotropy problem
matter-dominated universe
open universe
pair production
Planck era
Planck time
primordial fireball
quark
quintessence
radiation-dominated universe
strong nuclear force
superstring
universe
weak nuclear force