Astronomy Exam 2 Ch 6

telescope

a tool to gather light of all kinds and focus the light

two main types of optical telescopes

refracting, reflecting

refracting

use an objective lens to bend and focus light, suffer from chromatic aberration, human eye, can only be supported on both sides

chromatic aberration

light of different colors are focused at different points

reflecting

use a primary mirror and a smaller secondary mirror to focus light, all modern research telescopes, can be supported from the back

seeing

caused by turbulence and atmospheric distortions in the atmosphere, warm blobs of air rise, cooler blobs sink

what causes the stars to twinkle in the sky

seeing

what are not effected by seeing

telescopes in space

diffraction

quantum mechanical effect due to waves impinging on the edges of mirrors and lenses

we cannot achieve angular resolution better than

the diffraction limit

primary purpose of telescopes

gather as much light as possible

more photons means that

dimmer features are brighter and detectable

light buckets

telescopes

secondary benefit of a bigger telescope

better angular resolution

angular size of an object is used because

it is difficult to determine how big it is if you do not know the distance

1 degree

60 arc minutes (‘)

1 arc minute (‘)

60 arc seconds (“)

½ degree

moon’s angular size

angular resolution

the ability to distinguish two objects next to each other, ability to see fine/small detail

angular resolution of a telescope

the smaller the angular resolution, the ____ angular resolution is

better

pixel analogy: the smaller the pixel, the more pixels you can fit, more detail can be seen

for angular resolution

gamma rays and x-rays

wavelengths that earth’s upper atmosphere absorbs

what absorbs most UV light

ozone layer

why do telescopes get built at a high altitude

to avoid water vapor interference

Where is SOFIA (stratospheric observatory for infrared astronomy) and why

above the clouds to get above water vapor to be able to see the wavelengths

which bands of light are absorbed by the atmosphere

infrared and microwave

spectrographs

instruments used to separate light out by each wavelength into its individual components

objects that are spectrographs

prisms, diffraction gratings

diffraction gratings

optical component with a periodic structure that splits and diffracts light into several beams traveling in different directions.

instruments that record the image from a telescope

human eye and drawings, photographic plate, CCD

photographic plate

early, high-resolution imaging mediums consisting of light-sensitive emulsion (usually silver gelatin) coated onto glass or metal

CCD (charge-coupled devices)

highly sensitive, silicon-based electronic detectors that replaced photographic plates

particle accelerators

determine how particles and light behave