1.
Agenda: May 28th, 2013
1) Presentation groups get ready and leave to
classrooms
2) Warm-up – 5 min
3) Introduction to Galaxies – 10 min
4) Categorizing Galaxies Activity – 25 min
5) Present Findings – 15 min
6) Project Work time – 45 min
7) Exit Slip – 5 min

2.
Warm-up
Please answer the following questions on your
worksheet
1) What is a galaxy?
2) What do you know about galaxies?
3) What do you know about different types of
galaxies?

3.
Introduction to the Galaxy
What is a galaxy?
A galaxy is a cluster of billions of stars, dust, and
gas all held together by gravity. Galaxies are
scattered throughout the Universe. They vary
greatly in size and shape. Not all galaxies look
alike.

4.
This is a galaxy
This is a galaxy
This is also a galaxy
Did you notice how the galaxies don't look alike?

5.
When telescopes led to the discovery of galaxies,
astronomers observed many differences. In 1926,
an astronomer named Edwin Hubble decided to
classify the galaxies
He could have classified the galaxies by color, or
size, but he decided to classify them according to
shape

6.
This is also a galaxy
Did you notice how the galaxies don't look alike?
There are 3 main types of galaxies, starting with
the elliptical galaxies. Hubble used the letter “E” to
label elliptical galaxies.
Let's take a closer look at this type

7.
When telescopes led to the discovery of galaxies,
astronomers observed many differences. In 1926,
an astronomer named Edwin Hubble decided to
classify the galaxies
He could have classified the galaxies by color, or
size, but he decided to classify them according to
shape
Most galaxies are elliptical. Some elliptical
galaxies are circular, while others are extremely
stretched out. To deal with this variation, Hubble
divided the "E" classification into 8 sub-groups:
"E0", "E1", "E2", "E3", "E4", "E5", "E6", and "E7".
E0 galaxies are nearly circular in shape. While E7
galaxies are extremely
stretched out

8.
e1
Some examples
e3
e5

9.
Spiral galaxies
Hubble called the second type of galaxy you saw
a spiral galaxy. It reminded him of whirlpool. He
used the letter "S" to stand for spiral galaxies.
A difference between elliptical and spiral galaxies
is that spiral galaxies have a bright center, which
he called “nuclei”.
He classified galaxies with spiral arms into four
sub-groups that described how tightly the arms
were wound around the nucleus. Let's take a look

10.
S0(S-zero). Bright nuclei,
no arms
Sa: tightly wound arms
Sb: arms less tightly wound
Sc: very loose arms

11.
The third type of galaxy reminded Hubble of a
spiral with a solid bar across the center. He called
it a barred spiral galaxy. He used the letters "SB"
to stand for barred spirals.
Bar spiral galaxies

12.
In some spiral galaxies, the arms spiral out, not
from the center, but from a straight bar of stars,
gas, and dust that extends from both sides of the
bright nucleus. Hubble classified these barred
spirals into sub-groups "a" to "c" in order of
increasing openness of the arms
SBa SBb SBc

13.
Some galaxies don't fit either of these three
shapes, and are called irregular galaxies

14.
Edwin Hubble arranged the main types of
galaxies and the sub-types into a chart that has
come to be called "The Tuning Fork Diagram".

15.
Think you got it? You will now show what you've
learned by categorizing different galaxies into the
3 main types! Mr. Lee will give you your ziploc
bag and instructions.

16.
Project work time
We will spend the rest of the period working on
our science projects.
Please note that we will use the same classroom
rules: 1 warning for classroom noise, and after,
the individual or class will work in our textbooks.

17.
Please note
All non-presentation groups will be presenting in
our class on Friday. Your presentations only need
to be 1-3 minutes long.
Bernadette's group will present in Mr. Nemiroff's
class from 8:20-8:40am

18.
Please note
All non-presentation groups will be presenting in
our class on Friday. Your presentations only need
to be 1-3 minutes long.
Sammy's group will present in Ms. Miller's class
Friday from 10:35-10:55am