Post on 31-Dec-2015
How do How do colors in a colors in a spectrum spectrum help us help us
understand understand stars?stars?Image from
http://upload.wikimedia.org/wikipedia/commons/c/cd/Embryonic_Stars_in_the_Rosette_Nebula.jpg
Spectra Spectra and and
StarsStars
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We can’t go to stars and planets
to see what they are like.
So we learn about them
by studying the light that they emit or reflect.
Deep space image from http://upload.wikimedia.org/wikipedia/commons/2/21/Hubble_Ultra_Deep_Field_NICMOS.jpg
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Thinking about the spectra activity,
what evidence do you have that we can learn something about stars from their light?
1. From Activity 1 about adding light…….
2. From Activity 2 about using c-spectra and colored . filters…….
3. From Activity 3 about light from a hot gas………
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NASA: Spectroscopy in Action NASA: Spectroscopy in Action PLAY VIDEOPLAY VIDEO
https://www.youtube.com/watch?v=oRm0z8ggJSk
Visible light ranges in wavelength from ~400 to ~700 nanometers.
The color of light is the wavelength.
Image from http://science.hq.nasa.gov/kids/imagers/ems/visible.html
But visible light is only a small part of the electromagnetic spectrum.
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Waves only transfer energy without the physical movement of material from one location to another.
Light travels through space at 300,000,000 m/s.
One property of a wave is the wavelength – the distance between successive wave peaks.
Electromagnetic waves are transverse waves.
Image from http://upload.wikimedia.org/wikipedia/commons/5/5a/Crest_trough_wavelength_amplitude.png
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Light travels as a wave in an infinite
spectrum of electromagnetic radiation.
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Image from http://en.wikipedia.org/wiki/Microwave#mediaviewer/File:EM_spectrum.svg
The wavelength of an EM wave is inversely proportional to its frequency and also to it’s energy.
The shorter the wavelength, the higher the frequency and the more energy the wave has.
The range of all possible frequencies
of electromagnetic radiation is called
the electromagnetic spectrum.
Light is separated into its various wavelengths using a piece of glass called a prism.
A rainbow is an example of continuous spectrum.
Another Image that shows the experiment can be viewed at http://astronomy.nju.edu.cn/~lixd/GA/AT4/AT404/HTML/AT40401.htm
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CONTINUOUS SPECTRUM
Image from http://commons.wikimedia.org/wiki/File:Spectral_lines_continous.png
Occur when the light coming from a gas is passed through the surfaces of a prism or c-spectra. Depending on whether or not the gas cloud is in front of a blackbody object, the spectrum will either be an emission line spectrum or an absorption line spectrum.
Another Image that shows the experiment can be viewed at Image from http://astronomy.nju.edu.cn/~lixd/GA/AT4/AT404/HTML/AT40401.htm
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EMISSION & ABSORPTION SPECTRUM
Image from http://commons.wikimedia.org/wiki/File:Visible_spectrum_of_hydrogen.j
pg
Different Types of SpectraEach element has different emission lines which show the same colors that are missing in the absorption line.
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Another Image that shows a comparison can be viewed at http://www.extremetech.com/extreme/167878-every-color-of-the-suns-rainbow-why-are-
there-so-many-missing
Image from http://commons.wikimedia.org/wiki/File:Visible_spectrum_of_hydrogen.jpg and Image from http://commons.wikimedia.org/wiki/File:Spectral_lines_continous.png
Each atom of a given element is unique and has unique properties,
including what kind of color is emitted when it’s heated.
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Images from http://commons.wikimedia.org/wiki/File:Periodic_table_large.png
Hydrogen
What is the difference between Emission and Absorption Spectra?
The emission lines emit the color / wavelength.
Absorption lines absorb the same color / wavelength.
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Emission Spectrum
Absorption Spectrum
Image from http://commons.wikimedia.org/wiki/File:Visible_spectrum_of_hydrogen.jpg
Identifying Absorption Lines of a Star
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Image from http://upload.wikimedia.org/wikipedia/commons/d/d7/Cumulative-absorption-spectrum-hubble-telescope.jpg
Black lines are caused by gases on, or above, the Sun’s surface that absorb some of the emitted light.
The Mystery???? Some lines are not identified.
Are they produced by elements that don’t exist on Earth?
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Image from http://www.extremetech.com/extreme/167878-every-color-of-the-suns-rainbow-why-are-there-so-many-missing
Sun’s Absorption Spectrum
Ultraviolet (UV) light waves are invisible to the human
eye.
If we change the detector, we can ‘see’ these shorter wavelengths.
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Image from http://missionscience.nasa.gov/ems/10_ultravioletwaves.html
Ultraviolet Image of the Sun
X-ray detectors are used by scientists to see and record the energy within
the corona.
Data was collected by x-ray detectors
on satellites in orbit around the Earth by the Japan's
Hinode spacecraft.
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Image from http://missionscience.nasa.gov/images/ems/emsXRays_mainContent_xray-
sun.png
X-ray Image of the Sun
Used to study the light from planetary images and satellite imagery.
First telescope - Galileo in 1609. The eye detects visible light only.
Radio telescopes - detects the very longest wavelength of light.
Space Telescopes - detects different wavelengths, like X-ray, ultraviolet and infrared.
Space Telescopes - operate in space to avoid the obscuring effects of our atmosphere.
Chandra X-ray ObservatorySpitzer Infrared ObservatoryHubble Space Telescope - Optical
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Different Types of Telescopes and Detectors
Images from http://www.nasa.gov/mission_pages/