Studying the Universe

Telescopes

Telescopes aid astronomers in 2 ways• Gather more light than the naked eye

• Magnify images

Telescopes Best locations:

• Mountain peaksBecause of thinner air and high elevations

• Desert climatesDry, clear skies

• Remote areasNo city lights

Telescopes

Optical• Use lenses or mirrors to gather and

focus starlight• Kept in domes to protect from the

weather • Light gathering power depends on the

area of the lens or mirror

Refracting Telescope

Two lenses• Objective lens (end away from your eye)

Gathers starlight and bends it to form an image at the other end of the scope

• Eyepiece lens Magnifies the image for your eye

Reflecting Telescopes

One large curved mirror gathers and focuses starlight

The large mirror is the objective Has a secondary mirror to reflect the

image to the observer Also has an eyepiece lens to magnify

the image

Radio Astronomy

The study of radio waves given off by objects in space

Radio waves can pass through clouds of fine dust between stars (light rays can’t)

Can also be used during the day, when the stars can’t be seen

Radio Telescopes Look like satellite

dishes used for TV Made of solid metal

or wire mesh Collects and focuses

radio waves Radio waves have

longer wavelengths, so radio telescopes must be bigger than opticals

MMT

MMT = multiple mirror telescope

Several mirrors take the place of a single large mirror

Less expensive to build than single mirror

Hubble Space Telescope In orbit around Earth to

avoid clouds and be closer to far away objects

Misshapen main mirror and other mechanical difficulties made it less effective

Computers have provided image correction technology so the telescope can be used

Studying Energy

Stars emit light we can see….they also emit energy we cannot see

Electromagnetic energy – includes light, x-rays, radio waves, microwaves

Each type of energy has a different frequency and wavelength

All have the same velocity = 300,000 km per second

Electromagnetic spectrum = the range of wavelengths from radio

waves to gamma rays

Describing Energy Energy travels in waves… Frequency = the number

of waves that pass by a point in one second

Wavelength = distance from peak to peak or trough to trough

Frequency and wavelength are inversely proportional (as one goes up, the other goes down)

Visible Spectrum

Visible spectrum = the range of wavelengths we can see

Each color of the rainbow has a different wavelength and frequency

All of the colors of the rainbow make up “visible” or “white” light

Red has a long wavelength, which means it bends less when passed through a prism

Visible Spectrum

Spectroscope = a prism with a tiny viewing telescope

Separates light into its different colors

Spectrograph = prism with a lens and a camera, which records the spectrum

Visible Spectrum

Seeing the colors of light allow astronomers to determine which chemical elements are present in the star’s outer layers

Spectra also allow astronomers to determine if the star is moving towards us or away from us

Kinds of Visible Spectra

Continuous spectrum – unbroken band of colors, source is sending out all visible wavelengths of light

Can be produced from a glowing solid (light bulb)

Can be produced from a glowing liquid (molten iron)

Can be produced from the hot, compressed gases deep inside a star

Kinds of Visible Spectra

Bright line spectrum – unevenly spaced series of lines of different colors and brightness

Source emits only certain wavelengths of light

aka – emission spectrum Each element (as a gas) has a unique

combination of colors

Kinds of Visible Spectra

Dark line spectrum – continuous spectrum with dark lines where light is absorbed

Dark lines are in the same place as the bright lines

Form when light emitted by a star passes through a cooler gas

Gas absorbs the same wavelengths it would give off if heated

aka – absorption spectrum Used to identify the element

Emission spectra box Tube is filled with a

single element in the gaseous state

Electricity heats up the gas

The gas emits certain wavelengths of light

Combo of colors tells you what element you have