Name: ____________________________ Per: __________ Date: _______________    Score: ______/100

Redshift, Blueshift, One shift, Two shift

In the simplest terms, 'redshift' is a term used to describe the fact that the light seen from distant galaxies shows up a little differently than it does here on earth.  Each element has a 'fingerprint' in light.  This is how we know which elements are in which stars.  There is a certain pattern of lines associated with each element which identifies it, something like the bar codes you see on products in stores.  Each pattern or 'bar code' of dark lines shows up with a spectrometer at a specific place along the rainbow of visible light. However, as we get further and further out in space, these identifying lines, while keeping the same identifying patterns for each element, appear shifted somewhat to the red end of the spectrum -- thus causing the light to appear redder than it would be here on earth.

1. Based on the reading, what do you think a spectrometer does and why are they useful?

Use the reading and the data table to help you answer the next few questions

2. From the picture above and the reading, describe the evidence that the star clusters are moving away from Earth

3. In what way(s) would the spectrum data look different if the star clusters were moving towards earth?

4. What chemical symbol is used for the element, shown in the table above, that absorbs the two wavelengths of light? ________

5. How do you think astronomers were able to measure the speed that a star is travelling?

Part Two: The Electromagnetic Spectrum.

Redshift and blueshift describe how light (electromagnetic energy) changes as objects in space (such as stars or galaxies) move closer or farther away from us. The terms redshift and blueshift apply to any part of the electromagnetic spectrum. As objects are moving away from an observer, the light they emit will be red shifted or have a longer wavelength. As objects are moving toward an observer, the light they emit will be blue shifted or have a shorter wavelength. You just learned that from our observations of the universe, almost every other galaxy is red shifted!

1. Rank the 7 different types of electromagnetic energy from short wavelength to long wavelength in the ESRT

SHORTEST                                                                                                                                       LONGEST

2. What form of electromagnetic energy do your eyes see? _______________________

3. Light that is blueshifted to the maximum is known as Gamma Rays because this has the shortest possible wavelength. Using what you know about redshift and your ESRT, what type of electromagnetic energy is redshifted to the maximum? ___________________

4. When light is blueshifted it decreases in wavelength. When it is redshifted it increases. Complete the chart below for the different types of electromagnetic energy. The first three are done as examples.

Electromagnetic Energy (light)

Blueshifted

Redshifted

Blue (visible light)

Violet

Green

Yellow (visible light)

Green

Orange

X-Rays

Gamma Rays

Ultraviolet

Microwaves

Blue

Yellow

Infrared

Radio waves

Orange (visible light)

Violet (visible light)

Infrared

5. What form of electromagnetic energy does the Sun mostly output? Why do you think this?