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Light and TelescopesLight and Telescopes

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TopicsTopics

The Doppler Effect Extending Our Senses Summary

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The Doppler EffectThe Doppler Effect

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Fig. 2-14, p. 30

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Fig. 2-14, p. 30

Doppler Effect

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Fig. 2-16, p. 31

Discovery of Extrasolar PlanetsDiscovery of Extrasolar Planets

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Extending Our SensesExtending Our Senses

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Early MilestonesEarly Milestones

1608 – Hans Lippershey First telescope patent

1609 – Galileo’s observations of celestial objects Craters on the Moon Sunspots Phases of Venus Moons of Jupiter 1610 – Wrote 17th century best-seller:

Sidereus Nuncius (The Starry Messenger)

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Fig 3-1a, p.36

Galileo’sdrawingof theMoon

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Fig 3-2b, p.36

Galileo’s Observations of JupiterGalileo’s Observations of Jupiter

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Sidereus Nuncius, Sidereus Nuncius, G. GalileoG. Galileo

On the 7th day of January…..1610,….when I was viewing the constellations of the heavens through a telescope, the planet Jupiter presented itself to my view, and….I noticed a circumstance which I had never been able to notice before…..namely, that three little stars….were near the planet; and although I believed them to belong to the….fixed stars, yet they made me somewhat wonder, because they seemed to be arranged exactly in a straight line..

Galileo’s CommandmentEdited by Edmund Blair Bolles

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Fig 3-3, p.37

Phases of VenusPhases of Venus

Galileo’s discovery of the phases of Venus convincedhim that Venus orbits the Sun and not the Earth

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Fig 3-27, p.45

Broadening Our VisionBroadening Our Vision

Technology now exists that can record radiation spanning wavelengths from about 1 meter1 meter to 1 trillionth of a meter1 trillionth of a meter

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Optical TelescopesOptical Telescopes

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Characteristics of a TelescopeCharacteristics of a Telescope

A telescope is a device to “see far as if near”

To “see far as if near” a telescope must Gather radiation from an object (light, radio, x-

rays, etc.). How well this is done is called the telescope’s

Light-Gathering PowerLight-Gathering Power.

Resolve details of the object. How well this is done is called the

Angular ResolutionAngular Resolution.

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Light-Gathering PowerLight-Gathering Power

The amount of light gathered by a telescope is proportional to the areaarea of the collector.

A1 is the area of device 1

A2 is the area of device 2

If A2 > A1, then the light-gathering power of device 2 is A2 / A1 times greater than that of device 1.

Hubble Telescope Mirror

2.4 m mirror

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Light-Gathering Power: ExampleLight-Gathering Power: Example

D2 = 2.4 m

A1

A2

D1 = 6 x 10-3 m

A1 = (D1 / 2)2

A2 = (D2 / 2)2

pupil of human eye Hubble

AA22 / A / A11 = (D (D2 2 / D/ D11))22

= (2.4 / 6 x 10-3)2

= 1.6 x 105

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Angular ResolutionAngular Resolution

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Fig 3-5, p.37

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Fig 3-12, p.39

YerkesObservatory

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Fig 3-11, p.39

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Fig 3-21b, p.43

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Fig 3-13, p.40

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Fig 3-16, p.41

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p.34

HubbleSpaceTelescope(HST)

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Radio and X-Ray TelescopesRadio and X-Ray Telescopes

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Fig 3-33a1, p.47

KarlJansky

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Fig 3-36, p.49

The Very Large Array (VLA)The Very Large Array (VLA)

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Fig 3-29, p.45

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Fig 3-30, p.46

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SummarySummary

Doppler Effect Wavelengths increase increase, if separation between source

and receiver is increasingincreasing

Wavelengths decreasedecrease, if separation between source and receiver is decreasingdecreasing

Telescopes Gather as much radiation as possible Resolve as much detail as possible Now span the entire spectrum from gamma-rays to

radio-waves