Drawing Our Galaxy: Worksheet 1.2, Problem 1

Create an illustration of the Milky Way galaxy as viewed from outside the galaxy, viewed from the side and from above. You can draw by hand, or use a digital drawing tool such as Google Draw, Gimp or Illustrator. Post your illustration as a blog post, along with descriptive text of the figure. Your audience is a high school senior interested in astronomy, so don’t let them down with an obfuscated or incorrect description! Be sure to include the components in the list below. You may use any resource you find on the internet, but be sure that you have two sources for each bit of information you find so as to not post embarrassingly erroneous information. Wikipedia provides pretty solid information, but you should use library books, lecture notes, online books and/or Youtube videos as supporting information.
(a) Location of the Sun
(b) Thin/thick disks, bulge, halo
(c) Globular clusters
(d) The Small Magellanic Cloud (SMC) and the Large Magellanic Cloud (LMC)
(e) Sgr A* (Black hole)
(f) Location of Orion star forming region, and the nearest and furthest (known) open clusters to the Sun
(g) Scale length and scale height (in order to draw galaxy to scale)

Above we see a depiction - or at least an attempt at one - of our home. In astronomy 16, we focused on more immediate surroundings: stars and planets. In astronomy 17 we will be dealing with much bigger scales, and what better way to begin than with our home galaxy. The milky way galaxy is about 30 kilo-parsec in diameter, or at least most of the stars are within that diameter. There is also the "scale length" of the milky way to describe the width that contains the majority of the stars. The scale length is 3.5 kilo-parsecs and the scale height is 0.3 kilo-parsecs. Around the milky way there is a spherical halo, aptly named the halo, extending at least 40 kilo-parsecs and containing old stars, a little dust, and globular clusters (dense groups of stars).

In the middle of the galaxy lies the black hole Sgr A* with a radius of 22.5 million kilometers. Around the black hole is the bulge, made mainly of old stars, gas, and dust. Moving out from the bulge is the disk of the milky way. There is a thick disk that is about 1 kilo-parsec high and a thin disk about 300 pc high. This is where the spiral arms are located, with younger stars in the thin disk and older stars in the thick disk, on average.

We live in the Orion arm of the milky way, 8 kilo-parsec out from the center of the galaxy. Within one kilo-parsec of our sun (and therefore too nearby to fit in the diagram) lie the orion star forming region, Hyades, and Berkeley 29. The orion star forming region contains the orion nebula, a nursery for baby stars and one of the most photographed objects in space:

Source

Hyades is the nearest known open cluster - or a group of a few thousand stars that formed from the same molecular cloud - to the sun. It is about 47 parsecs away. The furthest known open cluster in the milky way is Berkeley 29 and is 15,000 parsecs away.

The Small Magellanic Cloud and the Large Magellanic Cloud are two galaxies in our milky way's neighborhood, or local group, that can be seen from the southern hemisphere. They are classified in some places as dwarf galaxies and in others as Magellanic galaxies: dwarf galaxies with one arm. The LMC is 50 kilo-parsecs away and 4.3 kilo-parsecs in diameter. The SMC is 61 kilo-parsecs away and 2.1 kilo-parsecs in diameter. 

Hope you enjoyed this tour of our neighborhood! Enjoy this complimentary map for all of you galactic travels.