Astronomers Observe

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Astronomers Observe

• Chris Stoughton
• March 16, 2002

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Observation

• Direct or indirect?
• Unaided or with instruments?
• Accidental or planned?
• Immediate or long term?
• Funding!

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First, a Tribute to William Herschel

• 1738-1822

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Discovery of Infrared Radiation
In the year 1800, Sir William Herschel
accidentallydiscovered the existence of
infrared radiation. NOTE you need to blacken
the bulb of the thermometer to get this to work.
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Parallactic Shift
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Uranus
It had actually been seen many times before but
ignored as simply another star. The earliest
recorded sighting was in 1690 when John Flamsteed
cataloged it as 34 Tauri.
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Herschels Milky Way
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The Galaxy
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The Milky Way in Different Wavelengths
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Herschel -- an Observer

• He made star counts, and found nebulae, etc.
• He analyzed these counts to make a picture of
  the Galaxy, as viewed from the outside
  indirect.
• He used an instrument, in fact, built his own.
• A famous discovery was made by accident.
• That got him funding!
• His planned observations, which took 20 years,
  led to a more profound result.

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Annie Jump Cannon

• Oh, Be A Fine Girl--Kiss Me!
• This phrase has helped several generations of
  astronomers to learn the spectral classifications
  of stars.

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At Work in Cambridge, MA
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Stellar Spectra
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Cecilia Payne-Gaposhkin
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Annie and her Colleagues

• Data Collection (direct observation) and Data
  Analysis (indirect observation) both have to be
  accomplished.
• Pickering had the observational horsepower to do
  fact accumulation but he did not appreciate the
  value of theory.
• Astrophysics brings down-to-earth physical laws
  to the sky.
• The flood of accidental observations turn out
  to make sense only after classification.
• Funding provided by Anna Draper led to the Henry
  Draper Memorial.
• Interpreting results using astrophysics yields
  enormous payback!

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The Big Bang

• A long time ago, the Universe we live in was
  incredibly small, dense and hot. Many different
  observations support this view and it now appears
  that the Universe underwent a very dramatic event
  right at the beginning, known as the Big Bang.
• Different estimates put the Big Bang some 13 to
  17 thousand million (13 - 17 billion) years ago.
• Since then the Universe has expanded, cooled down
  and has become much less dense.

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Observational Pillars

• Expansion of the Universe
• Origin of the cosmic background radiation
• Nucleosynthesis of the light elements
• Formation of galaxies and large-scale structure
• The Big Bang model makes accurate and
  scientifically testable hypotheses in each of
  these areas and the remarkable agreement with the
  observational data gives us considerable
  confidence in the model.

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Expansion of the Universe
Velocity H distance
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Cosmic Microwave Background
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Big Bang Nucleosynthesis
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Observational Cosmology

• The observations we make are indirect based on
  compiling a large number of direct observations.
• The types vary recessional velocities, spectrum
  of microwave noise, and the amount of Hydrogen,
  Helium, Deuterium, and Lithium.
• The instruments are a key here developing
  instruments is an important, and at times
  neglected, endeavor.
• Slipher accidentally saw (but did not realize
  it) that the Universe is expanding, while looking
  for ET.
• Cosmological observations are planned, and long
  term.
• Is the funding worth it?

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Industrial Astronomy -- SDSS
Cover ¼ of the sky Images of 300 million
objects Spectra of 1 million objects
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400 people 12 institutions
Data Collection will continue until June,
2005 The early data release is available at
skyserver.sdss.org, Along with educational
modules Please, if you want to help, use these,
evaluate them, and let us know How to improve
them!
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SDSS Web Sites

• http//www.sdss.org/ -- general information
• http//www.sdss.org/gallery/gal_zqso.html -- how
  quasars change with redshift
• http//skyserver.fnal.gov outreach and
  education
• Please critique and send your question, comments,
  complaints, praise, and bribes to me, Chris
  Stoughton, stoughto_at_fnal.gov