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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?
Ente
r ans
wer
text
...
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…
Brig
ht Neb
ulas
Glo
win
g Neb
ulas
Gre
y Neb
ulas
Dar
k Neb
ulas
0%
100%
0%0%
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?
Siz
e
Shap
e
Brig
htnes
s
Den
sity
11%6%6%
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?
Spira
l
Spira
l bar
red
Elli
ptical
Irre
gular
0% 0%
88%
12%
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?
Spira
l
Spira
l Bar
red
Elli
ptical
Irre
gular
5%
95%
0%0%
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?
A s
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up o
f sta
rs
Gia
nt gro
up of s
tars
l...
Neb
ulas
that
hav
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l...
0% 0%0%
1. A small group of stars
2. Giant group of stars located near the center
3. Nebulas that have collided
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