Electromagnetic Spectrum Symbols and Red Shift
Purpose:
What is the Electromagnetic spectrum? How do astronomers use the EMS to gain information
about the properties of the components of the universe?
Science 8- Astronomy
Red Shift
Astronomers view stars and galaxies with an instrument called a spectroscope. They use a spectroscope to
record the spectral lines that are shown here as dark lines on the visible spectrum.
These spectral lines are like a "fingerprint and can be
used to identify the elements that are present in a star or
galaxy.
Astronomers use spectral lines to determine if an object
is moving toward or away from an observer. They know
that as any source of light moves toward or away from an
observer, there is a shift in the wavelength of the light. For objects moving away, wavelengths are stretched
(lengthened) and the spectral lines shift toward the red end of the spectrum. This occurrence is appropriately
called redshift.
Redshift can also be used to determine the distance to a light source. Radiation from a distant source spends a
longer time traveling through space toward Earth and experiences a greater stretching of wavelengths.
Radiation from objects closer to Earth spends a shorter time traveling and wavelengths are not as stretched.
In the picture to the right, observe that a nearby galaxy
has a spectral line on the spectrum close to the middle.
A more distant galaxy has its line shifted toward the red
end and a very distant galaxy has its line shifted even
closer to the red end of the spectrum.
Questions:
1. Which example shows a nearby galaxy? C
A
2. Which example shows the galaxy which is the furthest
distance from Earth? B
B
3. Which example shows a galaxy which might be found at a
distance from Earth between the furthest and the nearest? A
C
4. Which color in the visible light spectrum has the longest wavelength? Red
5. How do astronomers use redshift to determine distances?
Radiation from a distant source spends a longer time traveling through space toward Earth and
experiences a greater stretching of wavelengths. Radiation from objects closer to Earth spends a
shorter time traveling and wavelengths are not as stretched.
6. Why does the presence of redshift in spectra of galaxies support an understanding of an expanding
universe?
Redshift indicates that wavelengths have been stretched as they move through lengthening distances
of an expanding universe.
Science 8- Astronomy