Transcript stars & galaxies

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?
Gas & Dust
Billions of stars
Liquids
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.
This Type of Nebula absorbs sTarlighT…
100%
Bright Nebulas
Glowing Nebulas
Grey Nebulas
Dark Nebulas
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JUST HOW MANY GALAXIES ARE THERE?
Space is that big!!!
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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?
Size
Shape
Brightness
Density
78%
6%
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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.
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…
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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?
Spiral
Spiral barred
Elliptical
Irregular
88%
12%
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Which type of galaxy has little or no shape
and tend to be smaller and fainter than
other galaxies?
Spiral
Spiral Barred
Elliptical
Irregular
95%
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The milKy Way…
our home iN The sTars…
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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…
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Within galaxies there
are star clusters.
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Open star clusters-is a
loosely shapes group
of stars. Found out
on the arms of a
galaxy.
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Globular clustershave 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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A small group of
stars
Giant group of
stars located
near the center
Nebulas that
have collided
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