ASTR 1200 Announcements

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ASTR 1200Announcements
Last Lecture on Thursday. Final Exam Wednesday
Dec 17 130-400 In Benson 180 Josh will hold
review 530-630 here (Benson180) On Monday (15th)
Website http//casa.colorado.edu/wcash/APS1200/AP
S1200.html
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A Modern Hubble Diagram
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Galaxies are Flying Apart
Galaxies remain same size. They just get farther
apart.
Effect is the same no matter which position you
occupy
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Expanding Universe
Current Universe
The volume of the universe is increasing.
Early Universe
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The Age of the Universe
Notice At time zero, d 0 All galaxies are at
zero distance! The universe has zero
volume! when t1/H
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Feeding a Quasar
Accretion disk is formed of stars and clouds that
wander too near the big black hole. Tidal forces
rip them apart. They settle into an accretion
disk. When theres no material falling in, the
quasar goes quiet.
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Jets
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The Cosmic Web
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Structure of the Universe
Where is the center of the Universe? Where are
the edges? What happens if you fly to the edge
and stick your finger through? Newtonian
Universe must be infinite. Cosmological
Principle The Universe is Everywhere the
Same (when averaged over grand scale)
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Classical Universe

• Euclidean Geometry
• Infinite in Extent
• Matter may or may not be everywhere
• Universe infinitely old
• always been here, always will be
• Expansion still possible
• 2 x 8 8

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Cosmological Principle

• Cosmological Principle applied to expanding
  Euclidean Universe
• New matter must be formed of nothing to keep
  density everywhere the same.

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Olbers Paradox
If universe is infinite with stars
everywhere, then there an infinite number of
stars. Any line of sight will eventually
intersect the surface of star. Sky would be as
bright as the surface of the Sun.
Well it isnt. So why not?
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Universe Must Change
Answer to Olbers Paradox Universe must
change Space ie the stars stop This was
the answer until mid 20th Century Time
Universe hasnt always been here, so cant see
forever. Discovery of Big Bang leads us to this
answer.
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General Relativity

• GR provided an answer
• The presence of matter warps space in on itself.
• Space is actually DEFINED by the presence of the
  matter in it!!!
• Solves the edge problem
• But geometry is no longer Euclidean

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Geometry of Universe
Space Curves in on itself Theres no path out!
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Curved Space
Surface of Earth has no end, but it is finite.
There is no edge but the volume is finite.
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Expands and falls back
Universe starts as pinprick Expands. But its
below escape velocity. Hits maximum size. Then
shrinks The End is the Big Crunch
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Negatively Curved Universe
Its warped so it cannot close back on itself. Is
infinite in extent.
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Open vs Closed
Universe is either open or closed.
If closed Positive Curvature Finite
Mass Finite Lifetime Finite Volume If
open Negative Curvature Infinite
Mass Infinite Volume Infinite Lifetime
Thats INFINITY Folks!!!
Astronomers have prejudice in favor of closed
universes. All measurements have been
inconclusive. We live near the edge!
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Critical Density

• Whether Universe is open or closed depends on the
  average DENSITY of matter.
• Above 10-29 g/cc the universe is closed
• Below 10-29 g/cc the universe is open
• We are very close to that density
• Coincidence?

rcrit is about 1 atom per liter
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History and Fate of Universe
Universe is one of these (maybe).
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Best Guess Size

• Diameter of Universe is about 1024 times larger
  than the part we can see.
• That makes the volume 1072 times larger.
• But still finite
• How big is 1072 ?

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Heat Death of Universe

• If universe is open, then it will last forever
• But stars will all burn out 1014 years
• Protons decay 1031 years
• Orbits will decay into black holes at center of
  the galaxies 1060 years
• Giant black holes evaporate 10100 years
• Nothing left but redshifting photons

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More on Infinite Universe

• If Cosmological Principle holds and universe is
  infinite, theres infinite mass.
• Infinite Planets
• Infinite Earth-like planets
• Infinite planets just like you.
• Infinite Yous
• Far away About

meters away
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The Origin of it All?

• Good Question
• Perhaps a bubble in a hyper-universe
• Perhaps its unknowable
• But it appears Universe started as a very tiny
  bubble. How small, we dont know.

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The Planck Era

• When quantum fluctuations exceed the radius of
  the universe our theories are definitely
  inadequate.
• R lt 10-35m
• t lt 10-44 seconds
• Density of Universe gt 1093 g/cc
• T gt 1032 K
• Then it starts to expand and cool.

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The Inflationary Universe

• Idea Vacuum of space-time created with excess
  energy ? folded upon itself
• At t10-37s, T1028K, starts to relax
• From 10-37 to 10-33s it expands by the creation
  of new space.
• Universe expands from 10-28m to 0.1m
• Thats 10cm in 10-33s 1032m/sv 3x1023 c !!!

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How Can It ExpandFaster than Light?

• Einsteins Law says nothing can travel faster
  than light.
• Particles in the inflationary universe arent
  traveling.
• More space comes into existence between them.
• Before inflation could see whole universe.
• Since then, can only see a small part.

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Big! Very, Very Big
Because of inflation, universe gets much bigger ?
A factor of 1026! Means now, universe is 1026
times larger than we can see. Rvisible
1026m Runiverse 1052m We are connected to
only one part in 1078 of the volume
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Maps of Microwave Background
The size of lumps and blobs set before
inflation. Indicate residual gravity from parts
of the universe we can no longer see. Strong
evidence that inflation is on the right track.
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The Annihilation Era

• After inflation settles down and resumes normal
  expansion
• So hot that matter and anti-matter are in
  equilibrium.
• For every 100,000,000 antimatter particles, there
  are 100,000,001 matter particles.
• Basic Asymmetry From Planck era is not
  understood, but its why were made of matter.

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.001 Seconds

• Jump from 10-33s to 10-3s
• T 1012K
• Neutrons and Protons now have cooled so that can
  annihilate with anti-neutrons and anti-protons.
• Leave mostly photons and an occasional particle
  of matter.

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1 Second

• Electrons and Positrons have cooled to point
  where they are no longer in equilibrium. T1010K
• Create photons.
• One matter particle in hundred million is left.
• Those are todays electrons.

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Era of Nucleosynthesis

• T 109 K
• t 100s
• Hydrogen and Helium form from neutrons and
  protons.
• Tiny amounts of Li and Be are created.
• No carbon density too low for triple alpha
• This is when the initial elements form

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The Plasma Era

• From 100s to 100,000 years universe is a soup of
  ionized hydrogen and helium
• But its expanding and cooling
• Ends at 100,000years when the temperature falls
  below 3000K.
• Hydrogen and Helium nuclei combine with electrons
  to form neutral atoms
• At that moment, universe becomes transparent

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Sky Aglow

• At moment of de-ionization, sky is glowing as
  blackbody at 3000K (M star)
• Photons released are no longer re-absorbed
• They travel into the universe and are travelling
  today
• But they redshift.
• Now 1000 times longer wavelength than then (makes
  them microwaves)

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The Cosmic Microwave Background

• Microwave Antenna at Bell Labs 1965
• Penzias and Wilson
• Microwaves coming from sky, but not Earth.
  Uniformly
• Predicted as part of a Big Bang by Gamov in the
  early 1950s
• Inescapable proof of the Big Bang
• Killed all steady state theories
• Now were studying it.

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At 100 Million Years

• No Galaxies yet or perhaps protogalaxies
• Gas mostly smooth through universe
• Clumps cause gravitational spots that create even
  greater density fluctuations.
• Size
• Remember Dark matter dominates

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Primordial Density Enhancements Grow

• Now (12.4Billion years) we have structure
• Galaxies and clusters

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Recap
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History and Fate of Universe
Universe is one of these (maybe).
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Dark Energy

• Expansion of Universe is Accelerating!!!
• Implies New Inflationary Era (Why Now?)
• Acceleration takes energy

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New Cosmology

• 70 of mass is Dark Energy (Emc2)
• 25 of mass is Dark Matter
• 3.5 of mass is in Intergalactic Medium
• 1.5 of mass is regular matter in galaxies
• Together they add to exactly critical density.
• Were right on the edge of open/closed
• Universe is either finite and very big, or
  infinite.