Week 6 Worksheet
Use the blackboard site to email me this assignment.
Deadline: Sunday, October 30th.
Phase 1:======Intro to Spectra and Spectrographs======
Phase 2:======Hubble Flow Experiment======
Question 1: Rank the following galaxies in the order of how fast they are moving away from us, from slowest to fastest. You do not need to know their exact speed, just whether they are the slowest to the fastest.
(Hint: Use the spectra and how far the Calcium line has been redshifted from its rest-wavelength of 3900 Angstroms.)
Question 2: Is there a relationship between distance to a galaxy and how fast it is moving away from us?
(Hint: Use the list of distances below to determine whether galaxies that are closer to us move more quickly away from us or whether galaxies that are farther from us move more quickly away from us.)
A) NGC 2903 is located 30 million light-years away from us.
B) NGC 3627 is located 36 million light-years away from us.
C) NGC 6643 is located 78 million light-years away from us.
D) NGC 2276 is located 100 million light-years away from us.
Note: The correct answer is that the further away the galaxy is from us, the more quickly it is moving away from us. I.e., NGC2276 is moving the fastest away from us and NGC2903 is moving the slowest.
Question 3: Explain how the result from Question 2 implies that the Universe is expanding.
Question 4: One model that astronomers use to visualize the expansion of the Universe is a stretchy band with galaxies lying along the band. As the band (the Universe) stretches, the galaxies move away from one another. The greater the distance between two galaxies, the more quickly they move away from one another.
Can you think of another model to help you visualize the expansion of the Universe?
Question 5: If everything is moving away from us, does that put us at the center of the Universe? Explain.
Question 6: Imagine playing the life of the Universe movie in reverse. Going backwards in time, instead of galaxies moving away from one another, they move towards each other. Explain how this implies a ‘Big Bang’.