The Electromagnetic Spectrum and information from the Stars

• X-ray image of the sun

Electomagnet (EM) Specrtrum

• All radiation, radio wave and light are part of the EM spectrum

• Visible light is only a very small section of the whole spectrum

Simpler version of the EM spectrum

Wavelength- Distance covered by one full cycle of a wave- commonly measured crest to crest

• CU physics site animation shows wavelengths

• http://www.colorado.edu/physics/2000/waves_particles/index.html

Relative size of wavelengths

Arecibo

• The Arecibo radio telescope in Puerto Rico is the largest single dish telescope in the world.

• This 1000 foot dish was constructed over a natural crater. (= 0.3km = 0.2 mi)

Radio antenna and radio telescopes are large to pick up long wavelengths

VLA

• The very large array in Socorro New Mexico was built in the 1970’s.

• It uses 27 radio telescopes all linked together in a Y shape. These telescopes simulate a large radio telescope 40 km in diameter.

The SETI Project

• SETI stands for the Search for Extraterrestrial Intelligence.

• SETI began using the Arecibo telescope to look for alien signals.

• In 1974 the Arecibo telescope sent a megawatt signal to outer space.

Frequency- How often a complete wave passes a set point

• Long wavelength = low frequency

• Short wavelength = high frequency

#waves/time = cycles/sec = Hertz (Hz)

Energy in the wave

• Long wavelength = low frequency = low energy• Short wavelength = high frequency = high energy

Fill in your own chart:

Spectra are created from excited electrons in atoms

• Valence electrons absorb energy from heat, electricity, other EM emissions

• Electrons jump up to a higher energy level

• When electrons “fall” back to ground state they give off EM emisions

Kinds of spectrum

• Continuous spectrum- like the rainbow

• Absorbtion Spectrum - has rainbow with “black” lines in it

• Emmission spectrum – just a line or two or three…………. Of colored light

Types of Galaxies- draw in

• Elliptical

• Spiral

• Irregular

Doppler Effect

• Red Shift-move away– Lengthen wavelength– Color shifts toward red

end

• Blue shift-move toward– shorten wavelength– Color shifts toward

blue end

Mass of the universe determines fate

• More than critical mass collapse Big Crunch another Big Bang?

Does the universe occilate? Closed universe

Less than critical mass expands forever Open universe

HR diagram

• Graphs starsTemp (color or spectral class) vs Absolute

magnitude (Luminosity)

Absolute magnitude – brightness based on being the same distance away from each star

Apparent magnitude – brightness from Earth- all stars are different distances away

HR Diagram

Temp degrees C

Put colored stars of appropriate size on your chart

Layers of the Sun

Micro-Wave & Infra-Red Telescopes

2 Famous Telescopes

• In the 1960” Robert Wilson & Arno Penzias won the Noble Prize for their discovery with the first large microwave telescope.

• COBE was a microwave / infra-red satellite in the 1980’s.

Visible “Optical” Telescopes

• Early history of optical telescopes.

• Modern day observatories.

• The future of optical telescopes.

Yerkes Observatory

• Built in 1897 the Yerkes telescope in Wisconsin is the largest refractor.

• It has 40 inch diameter lens!

The Mt. Wilson Hooker Telescope

• In 1908 the largest reflector telescope was built on Mt. Wilson overlooking Los Angeles.

• This Hooker telescope uses a 100 inch mirror to collect light.

The Palomar Observatory, Hale Telescope

• In 1948 the largest telescope was the 200 inch Hale telescope on Palomar Mountain, California.

The BTA Telescope

• Currently the largest single mirror telescope is the BTA, (Bolshoi Teleskop Azimutal) in Southern Russia.

• The BTA was built in 1975 and uses a single 230 inch mirror to collect light!

Multiple Mirror Telescopes

• After building the huge BTA telescope, astronomers realized that 200 inches is the maximum size for a telescope. Anything larger than 200 inches and the mirror becomes distorted under its own weight.

• The solution to this problem was to build multiple mirror telescopes.

Multiple Mirror Telescopes

• M.M.T. combine many mirrors to form one giant mirror. These mirrors are computer controlled to make a parabolic shape.

• The KECK telescope in Hawaii is currently the largest telescope in the world with a total of 400 inches of segmented mirrors!

3 Famous Observatories

• #1 Mauna Kea is Hawaii’s tallest peak and home to the largest telescopes in the world.

• #2 Las Campanas Chile has some of the clearest seeing on the the planet.

• #3 Kitt Peak Observatory in Tucson Arizona has a large collection of telescopes.

Mauna Kea, Hawaii

Las Campanas, Chile

Chile

The European Tel. In Chile

Kitt Peak, Tucson Arizona

Current Problems

• Aside from money, two of the biggest problems facing optical observatories are:

• 1. Light Pollution

• 2. Atmospheric turbulence

The Hubble Space Telescope

• By placing a telescope in orbit you solve the problems of light pollution and atmospheric turbulence.

• In 1990 the space shuttle Discovery was launched with the 90 inch Hubble Space Telescope.

The Future of Optical Telescopes

• The NGT (Next Generation Telescope) will be a 300 inch multiple mirror orbiting space telescope.

• The ELT will be a 30 meter (3 times larger than the Keck) segmented mirror telescope.

2 Plans for the NGT

LBT Large Binocular Telescope

One of the LBT mirrors

GSM Giant Segmented Mirror

ELT Extremely Large Telescope

Ultra-Violet Telescopes

• UV telescopes must observe from outer space.

• These telescopes specialize in observing the sun.

• The IUE is the International Ultra-Violet Explorer space telescope.

The IUE

The sun through the IUE

X-Ray Telescopes

• X-Ray telescopes study high energy objects like black holes.

• The Chandra X-Ray telescope was launched into space two years ago.

The Chandra X-Ray telescope

The Sun in X-Rays

Gamma Ray Telescopes

• Gamma Ray telescopes study very high energy objects like gamma ray bursters and supernova explosions.

• The Compton Gamma ray telescope was the most famous of these telescopes.

Compton Gamma Ray Telescope

The End