Transcript What is a Scientist? - Cockeysville Middle School

Objective: To define a light year in order to
describe the size of galaxies
Astronomy Note: How big are galaxies?
Drill: 1. Take out yesterday’s lab sheet.
2. Get a new ditto from the SET.
3. Complete Activity 1, #1.
ESS-3
on
e
Activity 1: Galaxy Recap
Open Your Textbook to page 145.
Read about our galaxy.
Brain Pop: Galaxies
ESS-3
on
e
Activity 2: What is a Light Year?
In order to understand the differences among
the various galaxies within the universe, you
need to understand the idea of “light years.” A
light year is a unit of distance equal to the
distance that light can travel in one year. Since
the speed of light is 300,000 kilometers per
second, light travels about 9.5 trillion
kilometers in one year. So, what does this
mean?
e
ESS-3
on
Activity 2: What is a Light Year?
Let’s think about it in a different way. For
example, if you were riding in a car traveling at
the speed of light, in one minute you could
travel over 11 million miles, in an hour over 660
million miles. At this speed, it would take you
about 100,000 years to go from one end of the
galaxy to the other (not counting gas and
munchie stops!).
ESS-3
on
e
Activity 2: What is a Light Year?
But, why would you want such a big unit of
distance, anyway? On Earth, a kilometer
measures distance just fine. For example, it’s a
few hundred kilometers from New York City to
Washington, DC, and it’s a few thousand
kilometers from California to Maine. However,
in the universe the kilometer is too small to be
useful.
ESS-3
on
e
Activity 2: What is a Light Year?
Think of it this way: the distance to the next
nearest galaxy, the Andromeda Galaxy, is 21
quintillion kilometers.
That’s 21,000,000,000,000,000,000 kilometers!
Obviously this number is so large that it is
difficult to write and interpret. Therefore,
scientists use light years.
ESS-3
on
e
Define light year, and explain why light
years are used in astronomy.
A light year is a unit of distance equal to
the distance that light can travel in one
year. We use light years in astronomy
because the distances are huge, so we
need bigger units to measure with.
ESS-3
on
e
Activity 3: Comparing Galaxies?
Chart 1: Sample Galaxy Characteristics
Characteristics
Milky Andromeda
Virgo A
Way
M32
Type of Galaxy
Spiral
Spiral
Elliptical
Elliptical
Diameter (light
years)
30,000
165,000
120,000
8,000
Est. # of Stars
within Galaxy
100
billion
200 billion
2.7 trillion
3 billion
Distance from
Milky Way (light
ESS-3
years)
2,700 billion
2,900,000
60,000,000 2,900,000
on
e
List the galaxies in order from smallest to largest.
a. M32
b. Milky Way
c. Virgo A
d. Andromeda
Pictures taken from space of the galaxies Andromeda,
Virgo A, and M32 show that Virgo A is the brightest
galaxy of the three. Explain why Virgo A would be the
brightest galaxy.
a. By far Virgo A has the most number of stars.
ESS-3
on
e
Activity 4: Quick Check
1. What is the name of our galaxy?
2. What characteristic do scientists use to
classify galaxies?
3. What does a light year measure?
4. What are the 3 categories for galaxies?
ESS-3
on
e
HOMEWORK:
1. In your Log Book, write at least 5 good
questions you currently have about
astronomy.
2. Complete Class Ditto.
3. Expert!!!
ESS-3
on
e