STARS & GALAXIES

Our Local System

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.

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.

What is a galaxy made of?

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100%1. Gas & Dust2. Billions of stars3. Liquids 4. Solids

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.

This type of nebula absorbs starlight…

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1. Bright Nebulas

2. Glowing Nebulas

3. Grey Nebulas

4. Dark Nebulas

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.

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

Galaxies are based on their what?

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78%1. Size2. Shape3. Brightness4. Density

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.

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.

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.

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

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1. Spiral 2. Spiral barred3. Elliptical 4. Irregular

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

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1. Spiral2. Spiral Barred3. Elliptical4. Irregular

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.

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.

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!

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

What is an open star cluster?

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1. A small group of stars

2. Giant group of stars located near the center

3. Nebulas that have collided

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