Telescopes II

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Telescopes II

• Dr Bryce

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Class Notices

• Homework due at 5pm

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Observing non-visible light

• A standard satellite dish is essentially a
  telescope for observing radio waves

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Radio Telescopes

• A radio telescope is like a giant mirror that
  reflects radio waves to a focus

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Radio telescopes

• To achieve good angular resolution, radio
  telescopes need to have very large diameter
• Hundreds of meters
• Thankfully the surface doesnt need to be
  completely smooth
• Although there is no light pollution but our
  communications are much louder than many
  astronomical sources

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IR UV Telescopes
SOFIA
Spitzer

• Infrared and ultraviolet-light telescopes operate
  like visible-light telescopes but need to be
  above atmosphere to see all IR and UV wavelengths

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Infrared

• Remember that we emit infrared radiation
• As does the Earth
• Even in space an infrared telescope needs a lot
  of cooling

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UV

• Much of the UV range behaves like visible light
  and can be collected by a mirror
• However extremely short wavelength and X-rays
  cannot be focused by mirrors, they require a nest
  of metal cones to focus the light using grazing
  incidence.

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Gamma Ray Telescopes

• Gamma ray telescopes also need to be in space
• Focusing gamma rays is extremely difficult
• We cannot locate the source of the rays without
  using other wavelengths

Compton Observatory
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Interferometry

• Interferometery is a technique for linking two or
  more telescopes so that they have the angular
  resolution of a single large one

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Interferometry

• Easiest to do with radio telescopes
• Now becoming possible with infrared and
  visible-light telescopes

Very Large Array (VLA)
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VLA
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VLBA
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The Sun

• Chapter 14
• (Yes we are skipping the missing chapters)

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Is it on FIRE?
Chemical Energy Content
10,000 years
Luminosity
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Is it CONTRACTING?
Gravitational Potential Energy
25 million years
Luminosity
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E mc2 - Einstein, 1905
It can be powered by NUCLEAR ENERGY!
Nuclear Potential Energy (core)
10 billion years
Luminosity
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Weight of upper layers compresses lower layers
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Gravitational or Hydrostatic equilibrium Energy
provided by fusion maintains the pressure
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Gravitational contraction Provided energy that
heated core as Sun was forming Contraction
stopped when fusion began
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Radius 6.9 x 108 m (109 times Earth) Mass
2 x 1030 kg (300,000 Earths) Luminosity
3.8 x 1026 watts