Lecture- tutorial: Milky Way Geography Oct 27
As you learn about different types of objects we see in the sky, we should ask if they are found in special places. In particular, we are going to explore how different objects are distributed in the Milky Way. Our first step is just to see in what direction we find them. The second step will be to ask how far away they are: this will require that we use some new methods besides the first one we learned: stellar parallax.
- Write a sentence describing what parallax is and how we measure it. Why is it only useful for nearby objects?
The attached list contains 100 objects that astronomers call Messier objects. The list way compiled by Charles Messier in about 1790: he was searching for comets, which appeared as fuzzy smudges in his small telescope. But he found a lot of other “smudges” that weren’t comets – and it’s these objects that he is best known for. In modern times, astronomers have classified these object. The list is ordered by the constellation in which the object was found, its number, and the modern description of the object. In particular, it includes open clusters, globular clusters, and galaxies (two types)
2.After looking at this list, do you expect that these three types of objects will be distributed randomly around the sky? Why or why not?
3. Use the attached print of the sky as it will appear on Nov 5 (when we are at Kitt Peak) and classify the number of different objects in each constellation that are visible that evening. (This is not how astronomers identify the position: we use a system similar to latitude and longitude on earth, and so we don’t pay any attention to the name of the constellation in which the object is found. But this will be easier for you in this exercise) Use the following system:
Filled circle for open clusters
Open circles for globular clusters
X for spherical or elliptical galaxies
4. When you have finished step 3, examine your sky print. Do you see any patterns? Discuss!
5. Based on what you concluded in step 4. Now look at the other constellations and the types of Messier objects they contain. You will want to use one of the Kitt Peak star wheels for this, as it has information about the Milky Way and where it runs. Can you make any further conclusions? Discuss!