Download BYOG: Build Your Own Galaxy

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BYOG: Build Your Own Galaxy
The purpose of this labette is to illustrate the major features of spiral galaxies. Those features are not accidents –
they are the result of the way the galaxy was formed, and they help explain how the galaxy behaves.
First, read the following description of galaxies (adapted from InfoPlease):
A typical spiral galaxy is shaped like a flat disk, about 100,000 light-years in diameter and just 1000 light-years
thick — about the same proportions as a standard CD. And, it has a central bulge and spiral arms. The bulge
contains old stars; but the arms winding through the disk contain dust, gas, and young stars. In a normal spiral
galaxy, the arms, at least two in number, join smoothly with the central bulge. The Milky Way has four major
spiral arms, named after the constellations that point to them: Perseus Arm, Sagittarius Arm, Centaurus Arm, and
Cygnus Arm (in order). Our Sun is about halfway out the Perseus arm on a side spur called the Orion arm.
Elliptical galaxies lack spiral arms entirely and contain little or no gas and dust, and resemble the nuclei of spiral
galaxies. Their shapes vary from nearly spherical to highly flattened ellipsoids. Irregular galaxies appear
structureless and without any nucleus or rotational symmetry; their light comes mostly from young stars.
The arms of spiral galaxies contain a larger number of bluer, younger stars, while elliptical galaxies and the
central bulge of spirals (as well as the spaces between the arms) contain a larger number of redder, older stars.
This has led astronomers to believe that stars initially cluster into spiral galaxies and that over time structural
changes transform them into elliptical galaxies.
Now, construct a model of a the Milky Way that includes the following features and uses the listed materials:
Empty
space
Black hole
Central
bulge
Spiral Arms
(4)
Old star
regions
(various)
New star
regions
(various)
Dust
Sun
15-cm black
disk
Marble (1)
Cotton balls
(3)
Cotton balls
(4)
Red & gold
glitter
Blue & silver
glitter
Pepper
Adhesive
Star
If available, label the arms with a glitter pen. Please do not over-use the glue, glitter and pepper – use only as
much as really needed, and always use the appropriate “glitter tray” to catch the extra. We will not have time to wait
for the glue to dry before adding pieces, so you’ll just have to be careful not to disturb your work as you go.
QUESTIONS:
1.
What materials would you NOT use if building an elliptical galaxy?
2.
The Andromeda Galaxy is our nearest neighbor, just 2.5 million light years away. That means that it’s about 25
galaxy diameters away from the Milky Way. How many centimeters would that be according to the scale we’re
using?
(Borrow a second galaxy and use a meter stick to place the models that distance apart.)
3.
Where in the galaxy do you think the stars will be closest together? Why?
Reversed image of the
spiral galaxy M-100,
about 55 million light
years away,
Dr. V / Physical Science
BuildYourOwnGalaxy.doc
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