ASTR 1200 Announcements Website Last Lecture on Thursday. Final Exam Wednesday Dec 17 1:30-4:00 In Benson 180 Josh will hold review 5:30-6:30 here (Benson180) On Monday (15 th )

A Modern Hubble Diagram

Galaxies are Flying Apart Galaxies remain same size. They just get farther apart. Effect is the same no matter which position you occupy

Expanding Universe Early Universe Current Universe The volume of the universe is increasing.

The Age of the Universe Notice: At time zero, d = 0 All galaxies are at zero distance! The universe has zero volume! when t=1/H

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 there’s no material falling in, the quasar goes quiet.

Jets

The Cosmic Web

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)

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 ∞ = ∞

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

Olber’s 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 isn’t. So why not?

Universe Must Change Answer to Olber’s Paradox: Universe must change: Space: ie the stars stop This was the answer until mid 20 th Century Time: Universe hasn’t always been here, so can’t see forever. Discovery of Big Bang leads us to this answer.

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

Geometry of Universe Space Curves in on itself There’s no path out!

Curved Space There is no “edge” but the volume is finite. Surface of Earth has no end, but it is finite.

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”

Negatively Curved Universe Its warped so it cannot close back on itself. Is infinite in extent.

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 That’s INFINITY Folks!!! Astronomers have prejudice in favor of closed universes. All measurements have been inconclusive. We live near the edge!

Critical Density Whether Universe is open or closed depends on the average DENSITY of matter. Above g/cc the universe is closed Below g/cc the universe is open We are very close to that density Coincidence?  crit is about 1 atom per liter

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

Best Guess Size Diameter of Universe is about times larger than the part we can see. That makes the volume times larger. But still finite How big is ?

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

More on Infinite Universe If Cosmological Principle holds and universe is infinite, there’s infinite mass. Infinite Planets Infinite Earth-like planets Infinite planets just like you. Infinite You’s Far away: About meters away

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 don’t know.

The “Planck Era” When quantum fluctuations exceed the radius of the universe our theories are definitely inadequate. R < m t < seconds Density of Universe > g/cc T > K Then it starts to expand and cool….

The Inflationary Universe Idea: Vacuum of space-time created with excess energy  folded upon itself At t= s, T=10 28 K, starts to relax From to s it expands by the creation of new space. Universe expands from m to 0.1m That’s 10cm in s = m/s v = 3x10 23 c !!!

How Can It Expand Faster than Light? Einstein’s Law says nothing can travel faster than light. Particles in the inflationary universe aren’t traveling. More space comes into existence between them. Before inflation could see whole universe. Since then, can only see a small part.

Big! Very, Very Big Because of inflation, universe gets much bigger  A factor of ! Means now, universe is times larger than we can see. R visible = m R universe = m We are connected to only one part in of the volume

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.

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 it’s why we’re made of matter.

.001 Seconds Jump from s to s T = K 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.

1 Second Electrons and Positrons have cooled to point where they are no longer in equilibrium. T=10 10 K Create photons. One matter particle in hundred million is left. Those are today’s electrons.

Era of Nucleosynthesis T = 10 9 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

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

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)

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 1950’s Inescapable proof of the “Big Bang” Killed all steady state theories Now we’re studying it.

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

Primordial Density Enhancements Grow Now (12.4Billion years) we have structure Galaxies and clusters

Recap

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

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

New Cosmology 70% of mass is Dark Energy (E=mc 2 ) 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. We’re right on the edge of open/closed Universe is either finite and very big, or infinite.