Optical telescopes Ones that use light energy

Functions of telescopes l Two uses l 1. Gather more light l 2. Magnify objects l Locations l 1. High elevations l 2. Dry climates l 3. Remote areas

Optical telescopes l Power depends on lens/mirror area l 1. Radius x 2 = 4x’s l Usually kept in a dome l 1. Protects from weather l 2. Controls temperature

Refracting telescopes l Simplest type l 2 lenses l 1. Objective l a. collects image l b. bigger size l c. bends light l 2. Eyepiece l a. smaller l b. magnifies l Most made before 1900’s

Refracting telescope Notice the size of people

Reflecting telescopes l Uses mirrors l like a periscope l Two types of manufacturing l 1. Solid piece ground and polished l 2. “spin cast” l a. spun while warm to curve wanted

Reflecting telescope Size is much larger

Multiple mirror reflections (MMT) l Uses several mirrors to simulate 1 large l Easier to maintain l VLT- very large telescope l m mirrors = 1-16m mirror in light gathering but 160m in resolution

Schmidt telescope l Located in most major areas l Utilize a combination reflecting and refracting l Used to take wide angle pictures primarily

Hubble telescope l Named after Edwin Hubble l Imperfect lens l 8’ diameter mirror l Contains spectrograph and infrared l Being replaced by the James Webb in 2015

Photographic plates l Allow for extended light gathering l Record positions of celestial objects l Comets found

Charge-coupled device (CCD) l More sensitive to light l Absorbs a broader spectrum l Photocells containing electrons are used l Electrons are stored in areas of high energy concentration

Comparison of photograph and CCD Photograph CCD

Electromagnetic spectrum l Energy waves traveling at 300,000 Km/s in space l separating types l 1. Use frequency and wavelength l a. frequency = # of waves passing a point per/sec l b. wavelength = dist from crest to crest l c. inversely proportional

Radio astronomy l Study of radio waves from space l Radio waves l 1. Lowest frequency (longest length) l 2. Received from areas that appear optically empty l 3. Unaffected by atmosphere and light conditions

Radio telescopes l Bowl shaped antennas l Receiver is located above and is movable l Larger than optical telescopes due to material used and wave sizes l 1. Steel mesh rather than glass l 2. Smallest is 26m l Largest is located in Puerto Rico

Puerto Rican telescope (Aricebo)

Radio telescope arrays l Use multiple units to simulate one large l 1. Distance between dishes = baseline l 2. 2 small at 100m = 1, 100m dish l Infererometry l 1.difference in arrival times to determine distance away l Increased baseline improves accuracy in details and depth

Example of use

Newest and bestest l Paranal observatory in Chilean mountains

Other wavelengths l UV, X-ray, and gamma rays are absorbed by the atmosphere l Studied with balloons, rockets and satellite l Located new items - Black holes, galaxies l Infrared telescopes l 1. Must be supercooled l 2. Located from any source of heat l 3. IRAS -located in space used liquid helium as a coolant (a short 10 month supply)

Major concepts (test material) l Function of telescopes l Types of telescopes (reflective, refractive, radio, infrared) l Use of arrays l Restrictions for infrared telescopes l Electromagnetic spectrum l Ways to improve images

Spectroscope l White Light is made of all colors l 1. Roygbv l Spectroscopes major parts are l 1. Prism- separates light l 2. Lens - focuses/magnifies light l 3. Camera - photographic plate or CCD

Major uses of spectroscope l Determine the following of stars l 1. Makeup / materials l 2. Temperature l 3. Pressure l 4. Magnetic field l 5. Condition of gases/ life stage

3 types of visible spectra Continuous Bright line Emmision Dark line absorption

Continuous l Unbroken band of colors l Can come from 3 kinds of materials l 1. Glowing solids l 2. Glowing liquids l 3. Hot, compressed gas

Bright line l Unevenly spaced series of lines of different colors and brightness l limited wavelengths are emitted l sometimes called emission spectrum l source- glowing gas or vapor l each element produces unique spectrum

Dark line spectrum l Continuous spectrum with dark lines where where light is absorbed l Also called absorption spectrum l Light passes through cooled gas, energy is absorbed by gas l Dark band are unique to each element

Uses for dark line spectra l Atmosphere of sun works as absorption filter l Determine planets atmosphere, if different than suns, the spectra will be different

The Doppler effect l Spectrum analysis noted shifts in bright line l Caused by movements to or from earth l 1. Red = increasing distance, longer wavelengths received l 2. Blue = decreasing distance, shorter wavelengths received

Major Concepts l 1. Use of spectroscope l Types of visible spectra l Doppler effect