Applications

1
Applications

• Collect more light. Depends on area of primary
  lens p(d/2)2 daperture

Eye/camera
d
eyepiece
Magnify. Power (focal length primary)
(focal length eyepiece)
telescopes are mostly used to collect more light
with angular resolution and aperture being
crucial criteria. Magnification usually not
important
2
Telescope Quality

• Light gathering
• bigger mirror
• sensitive electronic cameras
• can see dim objects lt 10-9 unaided eye
• Angular Resolution (or Vision)
• depends on mirror quality
• atmospheric turbulence limits to
• 1 arc second (1/3600 degree). But placing
  outside atmosphere or using correctable lens
  surface can reduce
• Hubble Space telescope and some on
• surface have 1/20 arc-second resolution

3
Detecting Light (not on tests)

• Human Eye
• cannot easily save information
• cannot collect light over long lengths of
  time
• Photographic Film
• -long time exposures-telescope needs to move
  opposite to Earths rotation
• -can filter to see different colors
• Electronic Devices (CCD, what is in video/digital
  cameras)
• -much more sensitive than film (1,000,000)
• -have amount of light versus time (instead of
  just sum). Can statistically remove effects of
  atmospheric twinkling or look for rapid
  variations
• -data easier to collect, to make available to
  others, to analyze

4
Vision

• Good angular resolution allows 2 close objects to
  be clearly separated. Same as good vision

Bad Resolution 3 times worse. Separate 4 objects
Good resoultion. See 12 objects
5
Telescope Quality

• Place at high altitude, away from cities, to aid
  in reducing atmospheric effects and light
  pollution (near Equator also good)

Mauna Kea Observatory on big island in Hawaii
including infrared. At 13,000 ft
6
Radio Telescopes

• Easy to make large. Atmosphere (including clouds)
  do not really effect
• angular resolution is worse as longer wavelength.
  Improve by making either with large aperture or
  fakinglarge using many dishes at same time

Very Large Baseline Array. 27 dishes in NM
Mass.
Use many spread out over continent/world
WV
Cal/NM
Puerto Rico
7
The Sun

• Some Properties
• Diameter - 109 times Earths
• Volume - about 1,000,000 times Earths
• Mass - about 300,000 times Earths
• Density Mass/Volume 1.4 g/cm3
• The Sun is a gas cloud of mostly Hydrogen and
  Helium
• Surface Temperature 5,800 degrees K
• Core Temperature 15,000,000 degrees K
• Age about 5 billion years

8
Energy Production in the Sun

• Sun produces
• 2 calories/cm2/minute at Earths surface
• 1011 cal/minute entire Earths surface
• 1027 calories/minute entire Suns surface
• Energy produced in the Sun flows out as light
  (and other EM energy).
• Equivalent energy units
• 4 times 1026 Watts
• 100 billion 1 Megaton Hydrogen bombs every
  second

9
Source of Suns Energy

• Big mystery before 1940
• Chemical Reactions do not give enough energy
• Gravitational energy can produce about 100
  million years at the Suns output but geological
  evidence shows Earth is billions of years old
• Need nuclear forces and reactions to power Sun.
  In particular, the strong nuclear force which
  holds protons and neutrons together