Agenda: May 28th, 2013

1) Presentation groups get ready and leave to classrooms 2) Warm-up 5 min3) Introduction to Galaxies 10 min4) Categorizing Galaxies Activity 25 min5) Present Findings 15 min6) Project Work time 45 min7) Exit Slip 5 min

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?

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.

This is a galaxy

This is a galaxy

This is also a galaxy

Did you notice how the galaxies don't look alike?

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

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

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

e1

Some examples

e3

e5

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

S0(S-zero). Bright nuclei, no arms

Sa: tightly wound arms

Sb: arms less tightly wound

Sc: very loose arms

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

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

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

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".

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.

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.

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

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

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