radiation & telescopes

Radiation & Telescopes

• ____________ radiation: Transmission of energy through space without physical connection through varying electric and magnetic fields

• Example: __________

Wave Motion

Label the WaveHow we see light video

_____________: Number of wave _______ that pass a given point per second__________: Time between passage of successive crestsRelationship:

Period = 1 / Frequency

Wavelength: ___________ between successive _________Velocity: __________ at which crests moveRelationship:

Velocity = ____________ / ________

No limit on wavelengths; different ranges have different namesNote opacity of atmosphere

Light and Color Bill Nye Video Part I

WavesThe Speed of Light in Glass Video

• Water waves, sound waves, and so on, travel in a ________ (water, air, …)

• Electromagnetic waves need ____ ____________

• Created by accelerating _________ particles

What is the wave speed of electromagnetic waves?

c = 3.0 x 108 m/s

This speed is very large, but still finite; it can take light __________ or even __________ of years to traverse astronomical distances

Telescopes

• ____________ lens

Images can be formed through reflection or refraction_____________ mirror

Modern telescopes are all _______________:• Light traveling through lens is refracted differently depending on ____________• Some light traveling through lens is absorbed• Large lens can be very _________, and can only be supported at edge• A lens needs two optically acceptable surfaces; mirror needs only one

Types of reflecting telescopes

The two 10-m telescopes of the Keck Observatory. (b) Artist’s illustration of the telescope, the path taken by an incoming beam of starlight, and some of the locations where instruments may be placed. (c) One of the 10-m mirrors. (The odd shape is explained in Section 5.3.) Note the technician in orange coveralls at center. (W. M. Keck Observatory)

The Keck telescopea modern research telescope

Sunrise on Mauna Kea in June

The _______ Space Telescope has a variety of detectors

Hubble Telescope image before and after it was fixed

Here we compare the best ______________ image of M100, on the left, with the ______ images on the right

Size• _________________ power: Improves detail

• Brightness proportional to square of radius of mirror

• Photo (b) was taken with a telescope twice the size of the telescope that took photo (a)

Size• Resolving power:

When better, can distinguish objects that are closer together

• Resolution is proportional to wavelength and inversely proportional to telescope size—bigger is better!

Figure 5-12. Detail becomes clearer in the Andromeda galaxy as the angular resolution is improved some 600 times, from (a) 10’, to (b) 1’, (c) 5”, and (d) 1”. (Adapted from AURA)

Atmospheric ___________ is due to ______ movements

Solutions:• Put telescopes on _____________, especially in __________• Put telescopes in _________•Why is it Dark at Night video

________ telescopes• Similar to optical reflecting telescopes• Prime focus• ______ sensitive to imperfections (due to ______ wavelength); can be made very _______ •Largest radio telescope is the 300-m dish at _________

________ wavelength means ________ angular resolutionAdvantages of radio astronomy:• Can observe ____ hours a day

• Clouds, rain, and snow _______ ____________

• Observations at an entirely ____________ frequency; get totally different ____________

Space BasedInfrared radiation can produce an image where visible radiation is __________; generally can use optical telescope mirrors and lenses

_________ telescopes can also be in space; the image on the top is from the Infrared Astronomy Satellite

The __________ Space Telescope, an ___________ telescope, is in orbit around the Sun. These are some of its images.

Ultraviolet observing must be done in ______, as the atmosphere absorbs almost ______ _____________ rays.

________ image of ___________ remnant

__________ rays cannot be ____________ at all; images are therefore __________

Full-Spectrum Coverage

Figure 5-36. Multiple Wavelengths The Milky Way Galaxy as it appears at (a) _____, (b) infrared, (c) ______, (d) X-ray, and (e) ____________ wavelengths. Each frame is a panoramic view covering the entire sky. The center of our Galaxy, which lies in the direction of the constellation Sagittarius, is at the center of each map. (NRAO; NASA; Lund Observatory; MPI; NASA)