Astronomy II, Fall 2005

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Astronomy II, Fall 2005 Lectures on galaxies and
cosmology
http//www.astro.gla.ac.uk/users/martin/basler/ast
ro2/
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Cornerstones of the Hot Big Bang Model
1. Expansion of the Universe
2. Background Radiation
3. Light Element Abundances
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Present Day
Big Bang
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Present Day
Big Bang
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Present Day
Big Bang
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Present Day
Big Bang
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From Lineweaver (1998)
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Value of
Scale factor of the Universe
Present-day
If the Concordance Model is right, we live close
to a special epoch. Why?
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The Big Bang
1920s - Georges Lemaitre proposes idea of a
primeval atom
Einstein not impressed! your calculations are
correct, but your physics is abominable
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The Big Bang
1920s - Alexander Friedmann develops non-static
universe models
Einstein not impressed! The results concerning
the non-stationary worldappear to me suspicious
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The Big Bang
Late 1940s 1950s George Gamow proposes hot
early Universe
with Alpher and Bethe predicts existence of
smoking gun relic radiation from the
primordial Universe
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predicted in more detail by Gamov, Dicke,
Peebles, in the 1950s and early 1960s
discovered in 1965 by Penzias and Wilson
Robert Dicke
Arno Penzias and Robert Wilson
Jim Peebles
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Cosmic Background Explorer (CoBE), launched 1989
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T 3K
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T 3K
Strong support for the Cosmological
Principle The Universe is homogeneous and
isotropic on large scales
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Early Universe too hot for neutral atoms
Free electrons scattered light (as in a fog)
After 380,000 years, cool enough for atoms fog
clears!
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CoBE map of temperature across the sky
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CMBR ripples are the seeds of todays galaxies
Galaxy formation is highly sensitive to the
pattern, of CMBR temperature ripples
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Microwave Anisotropy Probe
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From Bennett et al (2003)
First year WMAP results published 2003
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Another Big Bang prediction is that the lightest
elements were cooked during the first few
minutes. Their relative abundance today depends
on how much matter there was back then
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Another Big Bang prediction is that the lightest
elements were cooked during the first few
minutes. Their relative abundance today depends
on how many baryons were around back then
There is excellent agreement between the
predicted and observed abundances of the lightest
elements
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Another Big Bang prediction is that the lightest
elements were cooked during the first few
minutes. Their relative abundance today depends
on how many baryons were around back then
There is excellent agreement between the
predicted and observed abundances, but only if
the present-day numbers of atoms is about 1/7th
of the total matter density. But why dark
energy?...
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The future of the Universe-
No Big Crunch!!!