SS: Galaxies

• Physics
• Secondary Education
• Age 13

Forces and Motion

Lesson 14. 

Galaxies

How are you today?

😒🙁😐🙂😃

Highlights of the Day

•  describe a galaxy in terms of stellar dust and gas, stars and planetary systems

• Values :  Responsibility and Determination

Arrange me!

The 

Universe

star

solar system

planet

galaxy

moon

The Milky Way Galaxy

The word "galaxy" comes from the Greek word "galaxias" (γαλαξίας).

What does "galaxias" mean?

1. milk
2. milky
3. stars

How many major shapes of galaxies do we know that exist?

1. 1
2. 2
3. 3
4. 4

Shapes of Galaxies

Shapes of Galaxies

What shape of galaxy does the Milky Way Galaxy exhibit?

1. elliptical
2. spiral
3. peculiar
4. lenticular

Because we live in a spiral galaxy, we can only see one ‘arm’ of the spiral, which is that band across the sky. In fact, most of the stars we see at night are in our own galaxy. There are an estimated 250 000 000 stars in the Milky Way including our Sun.

Because we live in a spiral galaxy, we can only see one ‘arm’ of the spiral, which is that band across the sky. In fact, most of the stars we see at night are in our own galaxy. There are an estimated 250 000 000 stars in the Milky Way including our Sun.

TRUE or FALSE:
There are other galaxies in the universe besides our own.

1. TRUE
2. FALSE

TRUE or FALSE:
The word ‘planet’ is used to describe all of space and everything in it.

1. TRUE
2. FALSE

The closest known galaxy to the Milky Way is called the _________ Galaxy. It is elliptical in shape and a distance of away from us.

1. Canis Major Dwarf
2. Andromeda
3. Triangulum

What are galaxies made of?

Galaxies are made from stellar _________ , gas, stars and solar systems held together by gravity.

1. dust
2. fog
3. elements

Stellar dust is the dust that is found in space. The Earth is travelling through a cloud of stellar dust that is estimated to contain an average of one dust particle in every million cubic metres of space!

The gravity holding a galaxy together is very strong because galaxies are very large and have very large mass. Even if you could travel at the speed of light (300 000 kilometres per second), it would take you more than 100 000 years to cross from one side of the Milky Way to the other! Scientists estimate the mass of the Milky Way to be 1 500 000 000 000 times the mass of the Sun.

TRUE or FALSE
The gravity holding a galaxy is stronger than the gravity holding the planets in our solar system together.

1. TRUE
2. FALSE

How long will it take you to cross from one side of the Milky Way to the other?

1. 100 000 years
2. 1 000 000 years
3. 10 000 years

Approximately, how heavy is the Milky Way Galaxy?

1. 500 000 000 000 times the mass of the Sun
2. 1 500 000 000 000 times the mass of the Sun
3. 15 500 000 000 000 times the mass of the Sun

How many galaxies are there?

Scientists have counted the galaxies in one part of space. The scientists then multiplied this number up to estimate the number of galaxies in the universe. The answer they got was 

100 000 000 000 galaxies!

Self-survey: Rate your level of understanding and participation in this lesson.

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