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STARS & GALAXIES

Our Local System

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A STAR PARTY!!!The largest gatherings in the universe!

• Galaxies-Are large scale groups of stars that are bounded together by gravity.

• Size of a typical galaxy is 100,000 light years in diameter.

• Roughly 100 billion stars are contained within a galaxy.

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WHAT ELSE IS IN A GALAXY?The Nebula’s cometh.

• Galaxies also contain gases and dust.

• There are two bright nebulas.

• One glows bright from the hot gases within.

• Others shine by reflecting light from nearby stars.

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What is a galaxy made of?

1. Gas & Dust

2. Billions of stars

3. Liquids

4. Solids

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THE DARK SIDE OF THE NEBULA.The dark nebula.

• Other nebula’s are dark in nature.

• Dark nebulas are visible as dark areas among the stars.

• Dark nebulas absorb light of more distant stars behind them.

• The Horsehead Nebula is an example of a dark nebula.

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This type of nebula absorbs starlight…

1. Bright Nebulas

2. Glowing Nebulas

3. Grey Nebulas

4. Dark Nebulas

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JUST HOW MANY GALAXIES ARE THERE?Space is that big!!!

• Estimated 50 billion to 1 trillion galaxies in the known universe.

• The large Magellanic Cloud and small Magellanic cloud, are the closest to Earth’s galaxy; The Milky Way.

• These and other galaxies that are within 3 million light years of The Milky Way which number about 17 different galaxies are known as The Local Group.

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CAST OF GALAXIES…THE 3 MAIN TYPES OF GALAXIES.

• Galaxies can be classified into 3 different classes, based on their shape.

• The 3 types of Galaxies are;

• Spiral galaxies• Elliptical galaxies• Irregular galaxies

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Galaxies are based on their what?

1. Size

2. Shape

3. Brightness

4. Density

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SPIRAL GALAXIES…A SPINNER…

• Have a nucleus, or center, of bright stars.

• Outward from the center are flattened arms of stars that spiral around the nucleus.

• The spirals contain millions of young stars, gas & dust.

• Some spiral galaxies have a bar running through them. Known as a Barred spiral galaxy.

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ELLIPTICAL GALAXY…A FLASH IN THE PAN…

• Have shapes that range from nearly spherical to a flattened disk.

• Have very bright centers.

• Do not possess spiral arms.

• Do not have young stars and contain very little dust as gas.

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IRREGULAR GALAXIES…A LOT OF STARS WITH EGOS…

• Have no particular shape. Tend to be smaller and fainter than other galaxies.

• Could be formed from the collision of two different galaxies.

• Stars are of low mass and cannot organize into a pattern.

• Irregular galaxies are unevenly distributed throughout the universe.

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Which type of galaxy has a bright core but does not have not have young stars?

1. Spiral

2. Spiral barred

3. Elliptical

4. Irregular

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Which type of galaxy has little or no shape and tend to be smaller and fainter than other galaxies?

1. Spiral

2. Spiral Barred

3. Elliptical

4. Irregular

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THE MILKY WAY…Our home in the stars…

• Our galaxy is a spiral galaxy, in which the sun is one in a billion stars that are found inside.

• All the stars in the Milky Way have their own motion, some are moving towards the sun while others are moving away from our sun.

• Our sun is located on one of the spiral arms. It is rotating around the nucleus at 250 km/s.

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THE MILKY WAY…Our home in the stars…

• The Milky Way has a diameter of about 100,000 light years.

• The nucleus is 2000 light years thick.

• Our sun is located 30,000 light years from the nucleus.

• It takes the sun 200 million years to make one rotation around the center.

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Where is the Sun located in the Milky Way galaxy?

1. The galactic center

2. The perseus Arm

3. The orion arm

4. The outer rim

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THE MILKY WAY…Our home in the stars…

• You can look outside on a clear dark night and see the Milky Way!!!

• In the night sky it will appear as a band of stars that stretches across the sky.

• It will appear “milky” in the sky.

• You are actually looking at one of the arms of the galaxy!

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WHAT ELSE IS OUT THERE?The other objects in the night time sky…

• Within galaxies there are star clusters.

• Open star clusters-is a loosely shapes group of stars. Found out on the arms of a galaxy.

• Globular clusters- have a spherical shape and contain more stars than an open cluster. Found near the core of a galaxy

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What is an open star cluster?

1. A small group of stars

2. Giant group of stars located near the center

3. Nebulas that have collided

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IN A GALAXY FAR FAR AWAY…A STELLAR REVIEW PT 2.

• What is a nebula? A dark nebula?• Describe and draw a Spiral Galaxy.• Describe and draw an Elliptical Galaxy.• Describe and draw an Irregular Galaxy.• What type of galaxy is our Milky Way? Draw it.• Why is it called the Milky Way?• What are globular and open star clusters? Where are

they found?• What is a binary star system?