ThursdaySeptember 15,
2011
(Telescopes)
The Launch PadThursday, 9/15/11
How do galaxies evolve, and what holds them
together?Young galaxies are messy and random in shape. As they grow older, gravity
forms them into more organized shapes, like spirals or ellipses.
A strong gravity source holds them together, perhaps a massive black
hole at their cores.
The Launch PadThursday, 9/15/11
Which of the following would probably be the farthest from
Earth?A. the MoonB. the SunC. the Andromeda galaxyD. a large galactic cluster
Assignment Currently Open Page Date of Notes on Website Date Issued Date Due
ESS Class Information Sheet N/A N/A 8/24 8/25
Class Procedures and Expectations TBD 8/24 8/24 8/26
Lab - Stretching the Fabric of Space TBD 8/29 8/29 8/30
Quiz 1 TBD 9/6 9/6 9/6
Quiz 2 TBD 9/12 9/12 9/12
Optical (Visible Light) Telescopes
Optical telescopes are made in two basic types:
Refracting telescopes Reflecting telescopes
Refracting Optical TelescopesRefracting telescopes use a lens (called the objective) to bend
(refract) the light to produce an image.Light converges at an area called the focus.
The eyepiece is a second lens used to examine the image directly.
Refracting telescopes have an optical defect called chromatic aberration (color distortion.)
Reflecting Optical TelescopesReflecting telescopes use a concave mirror to
gather the light, and there is no color distortion.Nearly all large telescopes are of this type.
Appearance of a galaxy in the constellation Andromeda using
telescopes of different resolution.
The top picture is not “out of focus”, it’s a
resolving issue, not a focus problem.
Optical Resolution
Deployment of the Hubble Space Telescope in Earth Orbit
Figure 23.17
April 24,
1990
Other Types of TelescopesDetecting Invisible Radiation
Photographic films are used to detect ultraviolet and infrared wavelengths.
Most invisible wavelengths do not penetrate Earth’s atmosphere, so balloons, rockets, and
satellites are used to put the cameras above the atmosphere.
Ultraviolet Telescopes
Infrared Telescopes
Radio Telescopes
Radio wavelength radiation reaches Earth’s surface, so
radio telescopes can be Earth-based.
Radio TelescopesRadio telescopes are “big
dishes” used to gather radio wavelength electromagnetic
radiation.
Radio TelescopesRadio telescopes have to be very large in order to gather
radio waves, which are about 100,000 times longer than
visible radiation waves.They are often made of a wire
mesh, and have rather poor resolution.
Radio telescopes can be wired together into a network called
a “radio interferometer.”
A steerable radio telescope at Green Bank, West Virginia
Figure 23.15 A
Radio TelescopesRadio telescopes have several advantages over optical
telescopes: they are less affected by weather
they are less expensive to build and maintainthey can be used 24 hours a day
they are able to detect material that does not emit visible radiation
and, they can “see” through interstellar dust clouds
Radio Telescope Images
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