Universes & Galaxies
Cosmology - The Study of the Universe
Cosmology is the scientific study of the large scale properties of the universe as a whole. It endeavors to use the scientific method to understand the origin, evolution and ultimate fate of the entire Universe. Like any field of science, cosmology involves the formation of theories or hypotheses about the universe which make specific predictions for phenomena that can be tested with observations. Depending on the outcome of the observations, the theories will need to be abandoned, revised or extended to accommodate the data. The prevailing theory about the origin and evolution of our Universe is the so-called Big Bang theory.
Assignment 2 - Create an Illustration of the Milky Way Galaxy
Instructions: (Use the link above - Milky Way Notes/Reading to assist you)
Milky Way Galaxy Illustration
Part I. The objective of this assignment is to make 2 drawings of the Milky Way Galaxy in as good of detail as you can and learn the essential parts of our home in the universe. . .
Your drawing will include a top view and a side view, like:
Illustration needs to include:
1. Halo - include a simple drawing of how stars orbit in halo
2. Disc – show arrows for how stars orbit in halo
3. Bulge - include a simple drawing of how stars orbit in bulge
4. Sagittarius A
5. position of our solar system (Sun)
6. names of all the spiral arms – Perseus Arm/Carina-Sagittarius Arm/Orion Spur/Outer Arm/Norma Arm/Crux-Scutum Arm
7. globular clusters
8. a size scale in light years –
a.)distance edge to edge
b.)thickness of disk
c.)distance from Sun to center of bulge
d.) size of bulge in light years
Part II.
Check out: http://stars.chromeexperiments.com/
This is a tour of our area of the MWG,
Answer the following questions from your tour of the MWG:
1. How far away in light years is Voyager 1?
2. If you travel 1 ly away from the Sun, approximately where would you be?
3. Where do most blue stars live?
4. Name 5 of the closest stars to the Sun.
5. Toggle on the spectral index tool and observe the color of stars. . . what color are the majority of stars in a close in field of view?
Spiral Galaxy
A spiral galaxy is classified as an S galaxy with subclassification a, b, or c. The subclasses are divided based on the dominance of the bulge component of the galaxy. In Sa galaxies, the bulge dominates the galaxy, while in Sc galaxies, the bulge is much smaller. This is labeled on the SINGS Tuning Fork.
The appearance of the spiral arms also changes between the a, b, and c subclasses. In Sa galaxies, the arms are tightly wrapped around the bulge, while in Sc galaxies the arms are much looser, and often appear to be more clumpy than the smooth arms of an Sa galaxy. Sb galaxies have intermediate properties between those of Sa and Sc galaxies.
We can classify edge-on spiral galaxies based on the appearance of their bulge, even without being able to see the spiral arms. So for example, the edge-on spiral M104 - the Sombrero galaxy, seen below, can be classified as an Sa galaxy.
Barred Spirals
In some spiral galaxies, the bulge has a well-defined BAR that passes through the bulge. Hubble classified these galaxies by referring to them as SB galaxies with subclasses a, b, and c, just like the normal spirals. The spiral arms in barred spirals appear to originate at the ends of the bar, instead of in the bulge, like they do in normal spirals. We believe that the Milky Way is a barred spiral, perhaps an SBb or SBc type. The schematic image of the Milky Way that you studied in a previous lesson shows the Milky Way bar. Besides the presence of the bar, the properties of barred spiral galaxies are very similar to normal spirals.
Ellipticals
Elliptical galaxies (type E in Hubble's scheme) are featureless galaxies that appear to be just a ball of stars. They do not have obvious dust lanes and gas clouds like we see in spiral galaxies, either. There is no Hubble image tour of an elliptical galaxy, because there are no features to tour! With no gas and no dust, there are no young stars or star-forming regions seen in typical elliptical galaxies. The overall colors and spectra of elliptical galaxies are very similar to K stars, since they are dominated by these older, red stars.
The subclasses of the elliptical class are assigned numbers based on how round they appear. The roundest ellipticals are referred to as E0 galaxies, and the most elliptical-shaped galaxies that we have observed are labeled E7 galaxies.
Irregulars
Finally, we have the "miscellaneous" category. Anything that is so unusual that it can't be fit into any of the normal categories is called an irregular galaxy. There are two subclasses in this group, too. Irregular I galaxies (like the Magellanic Clouds) appear to have some spiral structure, but it appears to have been disrupted. Irregular II galaxies are much more disturbed than Irr I galaxies and look like they have been victims of some type of violent event that has completely disrupted their original shape. Many irregular galaxies are found to contain many young stars and to be experiencing significant ongoing star formation.
Assignment 3 - Galaxy Classification Exercise
Although Immanual Kant first advanced the idea of "island universes" to explain the observed compact clouds during the eighteenth century, it wasn’t until the late 1920's when Edwin Hubble began to develop an understanding of the nature of galaxies. The following is a chart and a sheet with fifteen galaxy photographs. Your task is to sort the galaxies using Hubble's classification scheme as seen on the Galaxy photo page. Complete the table using the 15 galaxy photos:
Review the information about the different galaxies and refer to the diagram to the right.
Hubble's Classification of Galaxies:
Edwin Hubble classified galaxies using the types that you see illustrated on the two tuning fork images; the one above and the SINGS image. His main types are:
Spirals,
Barred Spirals,
Ellipticals,
and Irregulars.
Within each of these groups, there are also sub-classifications.
Assignment 4:
Size/Scale of the Universe Virtual Assignment
Directions: Copy and paste the following link into Internet Explorer: http://htwins.net/scale2/. Click “Always Allow” for Adobe Flash. Choose “English” for language. Click the “Start” button to view the simulation.
This website will allow you to zoom in and out using the scroll bar on the bottom. You can click on objects for more information. The gray circle surrounding groups of objects are labeled with a measurement so that you know the general size of the objects.
Assignment 5: Complete the Spectrography/Doppler assignment: Use the resources below to help you with the understanding of how light is used in astronomy.
*Performance Task Guiding questions:
What is the purpose of your project?
What do you want others to learn from your project or presentation?
How can you apply/use the information or skills you learned in your life?
Bank of Experiment Examples (or you may choose your own).
Dirty Snowballs: Comet's size effects melting rate.
Star light, Star bright: Effects of light strength.
Space Race: Research/Time line of events.