Astronomy

Seeing through different light…

Visible UV..

Visible IR

Visible Radio Xray

Venus -IR

Venus -UV

Venus -RADIO

Venus -VISIBLE

Types of Light

• Gamma rays• X-Rays• UV rays• Visible Rays• Infrared• Microwaves• Radio• Long Waves

Types of Light

• Gamma rays– Nuclear blast

• X-Rays– Go through skin and body, stopped by bone

• UV rays– Penetrates skin, causes damage

Types of Light

• Visible Rays– What we can see

• Infrared– Night vision goggles

• Microwaves– Excite water

• Radio• Long Waves

Optical Telescopes

• Why do astronomers use telescopes?– Magnification– Resolution – Brightness

Brightness

• Gathering light to make faint objects appear bright

• MOST important• Depends on the size of

the lens

Resolution

• How sharp an object looks

• Larger the lens, higher the resolution

• HDTV vs. normal tv

http://upload.wikimedia.org/wikipedia/commons/f/f2/Resolution_illustration.png

Magnification

• How many times larger an object looks

• LEAST IMPORTANT

Magnification calculations

• M = fo/fe• Fo = Focal length of the objective• Fe = Focal length of the eyepiece

How big is our universe?

• MONTE PYTHON VIDEO

Optical Telescopes

Relflectors and Refractors

Refractors

• Uses lenses to bend light

Refractor

• Objective lens • Eyepiece

• Focal Length • The distance from a lens to the focal point

• Focal Point

• The point where light rays converge to produce an in focus image

Two lenses are placed at their focal lengths apart

• Fo (focal length of objective)• +• Fe (focal length of eyepiece)• =• Length of telescope

• Fo = 1000mm• Fe= 20 mm• What is the length of the telescope?

• What is the magnification?

Activity

• Right Eye Focal Length:

• Left Focal length:

• Both eyes

II. Focal Length of a lens

Focal Length of Lens 1:

Focal Length of Lens 2:

III. Magnification

• Draw a small arrow• Measure it in cm

Reflector Telescopes

Newtonian and Cassegrain

Newtonian Reflector

• Uses a mirror to reflect light

Newtonian Reflector

Cassegrain Reflector

• Has eyepiece behind mirror

• Has a small hole drilled into the middle of the objective mirror so that they light can go through

Cassegrain

Refractors

PROS• Better resolution due to no

diagonal mirror blocking part of the objective

CONS• Chromatic Abberation

(colors smear)• Size limit on objective lens

- if glass lens is too big it will sag)

• - max size = 3 feet

Reflectorss

PROS• No size limit

– The objective mirror can be made up hundreds of smaller mirrors

• Easier to hook up a computer to

CONS• Slightly less resolution

Optical observatories

• Keck 1 and Keck II in Hawaii

http://keckobservatory.org/images/gallery/telescopes/12_102.jpg

• Hubble Space Telescope

• GEMINI in Chili

Places to Build optical observatories

• Away from cities• Away from light pollution

• Mountain tops or space• The more atmosphere a telescope looks through , the

blurrier the image

Atmospheric Window

• Transparent to: Visible and Radio• Semi-Transparent to: Infrared• Opaque to: UV, X-Ray, Gamma Ray

Radio Telescopes

• Parts– Dish: :Large dish that focuses the rays (does

not have the be smooth)– Receiver: Gathers the rays and send to a

computer to analyze

• FALSE COLOR IMAGE: – Bright Areas= high intensity– Dark Areas= low intensity

RESOLUTION:

- Since radio waves are very large, they have very low resolution

Interferometer Array

• A way to increase resolution

• Observe the same object with lots of different telescopes

• Send all data to computer to create a high resolution image

Length of telescope

• Distance the telescopes are separated

Where to place Radio Telescopes

• Valleys– Avoids radio interference (mountains block the

signal)

Examples of Radio Observatories

• Arecibo– Worlds largest single radio telescope– Puerto Rico

• VLA– Very large array– New Mexico– On Train Tracks

• VLBA– Very large Baseline Arrary– Array of the worlds largest telescopes– Size of earth

Infrared Telescopes

• Uses regular mirrors• Must be placed high in the atmosphere

Sophia

• Aircraft with a telescope built in it

Spitzer

• In space• Studies stars and

planet formation

Telescope Videos

http://hubblesite.org/hubble_discoveries/hubble_deep_field/

Argon’s spectra

• The colored lines on the spectrum come from Argon’s electrons relaxing back to the ground state and releasing photons

• Fingerprint/Bar code

• Each element/compound has unique spectra

Hydrogen

• Less lines = less energy levels/electrons

Helium

Where should we put telescopes?