Download IDS 102

IDS 102
The Size of Astronomic Objects
An Atlas of the Universe
Go the website “An Atlas of The Universe” (http://www.atlasoftheuniverse.com/index.html).
This web page is designed to give everyone an idea of what our universe actually looks like. There
are nine main maps on this web page, each one approximately ten to twenty times the scale of the
previous one. The first map shows the nearest stars and then the other maps slowly expand out until we
have reached the scale of the entire visible universe.
The distances between astronomic objects are so large, that astronomers use their own measurement
system. Scroll down to the glossary and find the term “light year:”
 What is the definition of a Light Year:
 How many kilometers are in a light year?
 Given the information above, how many miles are in a light year (remember:1 km = 0.62 miles).
(Show your work below)
The definition of a light year also mentions other units. We will not be using “parsecs” in this class, but
we will mention “astronomic units”
 What is the definition of an astronomic unit (AU)?
 How do astronomic unit convert to the following?
1 AU =
km
1 AU =
mi
1 light year =
AU
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Now let’s set out a few definition. By definition, the universe is all of the matter and energy that we can
see or observe. We will be examining several smaller systems within the universe, so let’s set out
definitions for the following:
Galaxy:
Main sequence star:
Solar system:
Place the objects above in order from the smallest to the largest:
Smallest
Largest:
Now let’s go back to the main page and look at some maps. Click on the link for the map of “The Nearest
Stars” (12.5 Light Years from the Sun). Remember: you may need to scroll down to find the answers to
some questions.
 How many stars are shown on this map?
 What is the name of the closest star to our sun and how far away is it?
 Is this star bigger or smaller than our sun?
 What is the name of the brightest star in our night sky? How far away is it and how does it
compare in size to our sun?
Zoom out x20 to take a look at ‘The Solar Neighborhood” (250 Light Years from the Sun)
 How many star are within 250 light years of our sun and how many of the stars visible in our sky
are within 250 light years?
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Zoom out x20 and then x10 to take a look at our galaxy: The Milky Way.
 What is the scale of this map?
 How many stars are in our galaxy?
 What shape is our galaxy and how does the density of stars differ in different parts of our galaxy?
You will also need to look at the link for “A Map of the Milky Way” under additional link to answers
some of the questions below.
 Draw a sketch of the shape of our galaxy, include a scale bar that shows what the diameter of our
galaxy is.
 How does the thickness of our galaxy compare to its diameter?
Zoom out until you come to a map of “The Visible Universe.”
 What is the scale of this map and why does the universe appear to have this radius?
 Because light in the universe only travels at a fixed speed, we see objects at the edge of the
universe when it was very young.
 How long has the light from objects at the edge of the universe been traveling though space?
 How many galaxies (large and dwarf combined) and how many stars are there in the visible
universe?
If you would like to know more about the “Big Bang Theory,” click on the link at the bottom of the page.
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