electromagnetic spectrum in astronomy

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For Mr. Overbay's astronomy classes

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The Electromagnetic Spectrum in Astronomy : 

The Electromagnetic Spectrum in Astronomy

Slide 2: 

Wavelength (length/cycle) Amplitude: wave height = brightness Amplitude trough crest Properties of Waves All electromagnetic waves travel at the same speed The speed of light: 300,000,000 m/s

Light as a Wave : 

Light as a Wave Light waves are characterized by a wavelength and a frequency c = 300,000 km/s = 3108 m/s l

Frequency, wavelength, energy : 

Frequency, wavelength, energy Wavelength and frequency are inversely proportional Long wavelength-lowest frequency Short wavelength highest frequency Frequency and energy are directly proportional The higher the frequency the higher the energy.

Wavelengths and Colors : 

Wavelengths and Colors Different colors of visible light correspond to different wavelengths.

VISIBLE LIGHT : 

VISIBLE LIGHT Electromagnetic waves we can see. Longest wavelength= red light Shortest wavelength= violet (purple) light When light enters a new medium it bends (refracts). Each wavelength bends a different amount allowing white light to separate into it’s various colors ROYGBIV.

Slide 7: 

Solar Spectrum The sun emits radiation at all wavelengths Most of its energy is in the IR-VIS-UV portions of the spectrum ~50% of the energy is in the visible region ~40% in the near-IR ~10% in the UV Wavelength (m)

Earth’s atmosphere is transparent to certain wavelengths : 

Earth’s atmosphere is transparent to certain wavelengths

Light as Particle : 

Light as Particle Light also behaves like a particle This particle is called a photon The energy of a photon is dependent on its frequency A photon is like a little packet (quantum) of electromagnetic energy.

Where do photons come from? : 

Where do photons come from? Photons come from atoms Atoms absorb and emit photons at certain specific frequencies. This is because the electrons can only be in certain orbitals.

Atomic Emission : 

Atomic Emission

This means… : 

This means… Because electrons can only be in specific orbitals, only specific frequencies are emitted or absorbed. Atoms of an specific element absorb or emit only specific frequencies of electromagnetic energy. This is called the absorption or emission spectrum.

Using this in astronomy : 

Using this in astronomy Astronomers can use these spectra to determine the composition of stars and planets and other stellar objects.

The Sun’s Emission Spectrum : 

The Sun’s Emission Spectrum

Spectroscopy : 

Spectroscopy Using wavelength/frequency to determine composition Can use light emitted emission Or light absorbed absorption

Light and temperature : 

Light and temperature Electromagnetic spectrum also tells temperature More heat = more energy More energy = higher frequency Higher frequency = More heat

Thermal radiation : 

Thermal radiation electromagnetic radiation emitted an object because of the object's temperature

Temperature of Stars : 

Temperature of Stars Gamma and x-ray emitters are hottest Blue stars are hotter Red stars are colder Radio emitters are coldest

Kelvin : 

Kelvin Kelvin is the astronomer’s temperature scale Abbreviation : K K= ºC + 273 So… 0K = -273ºC

What’s colder than cold? : 

What’s colder than cold? Absolute zero! 0K Absolutely NO atomic motion None Nada Zip Zilch No not even a little. Deep space is just a few degrees above absolute zero

Manipulating Light : 

Manipulating Light Manipulating, or working with, light is what astronomers do We have two main ways to manipulate light: Refraction Reflection

Refraction : 

Refraction Changing the direction of light as it passes through some medium For example: Straw in drink lenses

Refracting Telescope : 

Refracting Telescope Focus light through a series of lenses Like what Galileo used

Reflection : 

Reflection Redirection of electromagnetic radiation Can be done with more than just visible light!

Reflecting Telescopes : 

Reflecting Telescopes Focus light through a series of mirrors Invented by Isaac Newton

Reflecting Telescopes : 

Reflecting Telescopes Allow for larger telescopes English astronomer William Herschel built this huge reflecting telescope in the late 1700s.

Radio Telescopes : 

Radio Telescopes Work like visible light reflector scopes Use the radio frequencies

Radio Telescopes : 

Radio Telescopes

Radio Astronomy : 

Radio Astronomy Cassiopeia A in visible light Cassiopeia A in radio

Infrared Astronomy : 

Infrared Astronomy Infrared can’t get through the atmosphere Spitzer Space Telescope uses infrared to see an optically invisible universe dominated by dust and stars. Lyman Spitzer Jr.

Infrared Astronomy : 

Infrared Astronomy

X-Ray astronomy : 

X-Ray astronomy X-rays also cannot get through the atmosphere The Chandra X-Ray Observatory observes X-rays from high-energy regions of the Universe. Subrahmanyan Chandrasekhar

X-Ray astronomy : 

X-Ray astronomy Galaxy M-101 in visible Galaxy M-101 in X-rays

One Object, Different Wavelengths : 

One Object, Different Wavelengths