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Observational Cosmology. Jonathan P. Gardner NASA’s Goddard Space Flight Center. Wilkinson Microwave Anisotropy Probe. Gary Hinshaw, WMAP Co-I. University of Edinburgh, September 3, 2004. Hubble Space Telescope. James Webb Space Telescope. Astronomical Search For Origins. First Galaxies.

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observational cosmology

Observational Cosmology

Jonathan P. Gardner

NASA’s Goddard Space Flight Center

wilkinson microwave anisotropy probe
Wilkinson Microwave Anisotropy Probe

Gary Hinshaw, WMAP Co-I

University of Edinburgh, September 3, 2004

astronomical search for origins
Astronomical Search For Origins

First Galaxies

Big Bang


Galaxies Evolve



beginnings are important origins
Beginnings are Important …(Origins)

David Jonathan Gardner, June 16, 2005

David Jonathan Gardner, June 16, 1998

... So Are Changes(Evolution)

the first 13 7 billion years
The First 13.7 Billion Years

Dark Matter/Dark Energy

Galaxies Evolve

Planets, Life & Intelligence

First Galaxies

Atoms & Radiation:CMB

Particle Physics

Big Bang


3 minutes

380,000 years

400 million years

1 billion years

7 billion years

13.7 billion years

edwin p hubble the man not the telescope
Edwin P. Hubble(the man, not the telescope)
  • Classification of Galaxies
  • The “Spiral Nebulae” are “Island Universes”
  • The Universe is Expanding

Edwin P. Hubble, 1889-1953

Which is further away?How can you tell?

the hubble sequence
The Hubble Sequence
  • Hubble classified nearby (present-day) galaxies into Spirals and Ellipticals.
  • The Hubble Space Telescope extends this to the distant past.
measuring distances
Measuring Distances

Cepheid Variable Stars: known period-luminosity relation.

Astronomers can measure distances if they know the intrinsic luminosity.

Suitable for nearby galaxies

Supernovae: known maximum luminosity. Suitable for distant galaxies.

hubble discovers the universe
Hubble Discovers the Universe

Cepheids in the Andromeda galaxy showed it is 8 times further than the most distant star in our Galaxy.

 Island Universes!

Hubble at Mount Wilson telescope

“Planetary Nebula” are within our Galaxy.

hubble s law
Hubble’s Law

Velocity in Kilometers per Second

looking backwards in time
Looking Backwards in Time

Far, Far Away means Long, Long Ago

Distance + Light travel time = Seeing the past.

1 Billion light years away

1 Billion years ago


1 Million light years away,

1 Million years ago

Here & Now



The Horizon Problem

Why is the cosmic microwave background

temperature so uniform on scales >2°?


= T

+ O (10













D >> c/H


q >> 2




The Flatness Problem

Why is the universe anywhere close to W =1 now?


W =1 is an unstable stationary point.


Density 1ns after BB

447,225,917,218,507,401,284,015 gm/cc

Scale Factor a(t)

447,225,917,218,507,401,284,016 gm/cc

447,225,917,218,507,401,284,017 gm/cc




t [Gyr]


curved space time
Curved Space-Time

Flat, or Euclidean Space

Negative Hyperbolic Space

Positive Spherical Space

3D Figures by Stuart Levy of the University of Illinois, Urbana-Champaign and by Tamara Munzer of Stanford University for Scientific American. 2D Figures by Ned Wright, UCLA


The Structure Problem

Clumpy distribution

of galaxies -

how did this happen?

Smooth 3K

Cosmic microwave

background radiation


inflation solves the problems
Inflation solves the problems

Later, the regions re-enter the horizon.Quantum fluctuations become galaxies

Before Inflationcausally connected quantum fluctuations.

After Inflation,previously connected regions are outside the horizon.

Predictions: Universe is flat. Fluctuations are correlated on different scales.


Synthesis of Light Elements

  • Light elements, D, He, Li produced ~3 minutes “after Big Bang”.
  • One free parameter in predicted abundances: baryon/photon ratio
    • (note: baryons = atoms)
  • Baryon/photon ratio now measured by CMB (discussed later).
  • Predicted abundances may now be confronted with observed abundances (grey boxes). Some tensions.
the first 380 000 years
The First 380,000 Years

Wayne Hu and Martin White, Scientific American, February 2004

why bright clumps remnants of primordial oscillations
Why Bright Clumps?Remnants of Primordial Oscillations

Gravity tries to

make matter fall

into potential wells

Radiation pressure

pushed back...

Oscillations results…

Imprint of event

imparted on photons...

wmap shows the universe is flat
WMAP shows the Universe is Flat

Dark Matter



the first 400 million years
The First 400 Million Years

Cooling with atoms

Cooling with H2

Barkana & Loeb 2001, Physics Reports, 349, 125

the first galaxies
The First Galaxies
  • What did the first galaxies to form look like?
    • They are very distant, and very faint.
infrared light
Infrared Light
  • Most of the Sun’s energy is visible light
  • Light from the first galaxies is redshifted from the visible into the infrared.
  • Infrared is heat radiation
deepest view s of the universe
Deepest View(s) of the Universe
  • 1995 Hubble Deep Field
    • 10 days exposure, small area
  • 1998 Hubble Deep Field South
    • Repeat in another field
  • 2003 Great Observatories Origins Deep Survey
    • 30x area
    • infrared with Spitzer, X-ray with Chandra
  • 2004 Hubble Ultra-Deep Field
    • 30 days exposure, more sensitive camera
  • 1996-2006-… Follow-up observations

Hubble Ultra Deep Field

finding distant galaxies


Finding distant galaxies
  • UV radiation shortward of Lyman limit at 912Å is absorbed by inter-galactic medium.
  • This break is redshifted through successive filters
  • Visible light technology (CCDs) ends at ~1 micron, so finding galaxies at z>6 requires infrared.
history of star formation in the universe
History of star-formation in the Universe

Star-formation density

Bouwens et al. 2005, astro-ph/0509641

prospects for future study at high z
Prospects for future study at high-z
  • Hubble (2.4m diameter warm telescope):
    • Reaches to z~6, with claims to 7 or 8.
    • New camera to be installed in next servicing mission may reach to magnitudes of 28.5 (15 nJy) in the NIR.
    • No longer has sensitive spectroscopic capability in opt-NIR.
  • Spitzer (0.85m diameter cold telescope):
    • Reaches to z~6 (same galaxies as HST).
    • Reaches magnitudes of 26.6 in near- to mid-IR.
  • Ground-based observations (10m warm)
    • Limited by atmosphere
how to win at astronomy


How to win at Astronomy


Photographic & electronic detection


Telescopes alone



Big Telescopes with Sensitive Detectors in Space


Sensitivity Improvement over the Eye








Rosse’s 72”

Mount Wilson 100”

Mount Palomar 200”

Soviet 6-m

Short’s 21.5”

Herschell’s 48”

Slow f ratios









Adapted from Cosmic Discovery, M. Harwit

Year of observations

hst vs jwst temperature
HST vs. JWST - temperature

-225° Celsius,-370° Fahrenheit

Room Temperature

hst vs jwst orbit
HST vs. JWST - orbit

How will JWST get there?

375 miles up

Second Lagrange Point,1,000,000 miles away

Ariane 5

hst vs jwst size
HST vs. JWST - size

How do you put a 6.5 meter mirror in a 5 meter rocket?

2.4 meter diameter

6.5 meter diameter

when was re ionization


Neutral IGM








Lyman Forest Absorption

Patchy Absorption

Black Gunn-Peterson trough

When was re-ionization?

Fan et al. 2001, AJ, 122, 2833

Fan et al. 2001, AJ, 122, 2833

Kogut et al. 2003, ApJS, 148, 161

distant galaxies are train wrecks
Distant Galaxies are “Train Wrecks”
  • Trace construction of Hubble sequence:
  • How do “train wrecks” become spirals and ellipticals?

By Merging!

the next 20 years
The Next 20 Years
  • What is the cause of inflation?
  • What is the dark energy?

In other words:

  • How did the Universe begin?
  • How will it end?
can we prove inflation
Can We Prove Inflation?
  • Gravity waves propagating during inflation leave a mark on the polarization of the CMB.
  • CMB Polarization mission
    • Currently being studied.
what is the dark energy
What is the Dark Energy?
  • Hypothesized by Einstein, discovered in 1998, confirmed in 2003.
  • 3 potential Nobel Prizes:
    • Cosmological Constant breaks standard model of particle physics
    • Quintessence means new physics
    • Modification of General Relativity
  • NASA-DOE Joint Dark Energy Mission
    • Currently being studied.
observational cosmology1

Observational Cosmology

Jonathan P. Gardner

NASA’s Goddard Space Flight Center