Transcript Galaxies - Mister Mac`s Science Class

Galaxies
- Group of stars, gas, and dust.
- There are over 40 billion galaxies in the universe!
- 1000 to 1,000,000 light years wide.
Mr. Mac’s Earth Science Classroom
New Vocab Worddddd….
Light Year (ly): distance light travels in one year.
A light year is not a measure of time.
Light travels 9.5 trillion kilometers in one year. That’s a lot!
Star: 4.3 ly away 
It will take light 4.3
years to reach our
eyes. (Proxima
Centauri)
Mr. Mac’s Earth Science Classroom
What is a galaxy?
Spiral Galaxies
Elliptical Galaxies
Irregular Galaxies.
Mr. Mac’s Earth Science Classroom
Spiral Galaxies
Pinwheel
Shape
Rotation
Halo of old
stars
Spiral Arms
lots of
gas/dust
Central
Bulge little
gas/dust
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Elliptical Galaxies
Ball
shaped
Mostly
old stars
Halo of
old stars
Very little
gas/dust
Most are
very tiny
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Elliptical Galaxies
Most are tiny
Mr. Mac’s Earth Science Classroom
Irregular Galaxies
Irregular
Shape
Active and
Volatile
Conditions
Lots of gas
and dust
D. Hunter (Lowell Observatory), Z. Levay (STScI)
Lots of
stars
forming
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Irregular Galaxies
These galaxies are not spiral or elliptical.
They are irregularly shaped.
They contain lots of gas and
dust which means that lots of
stars are forming.
Local Group Galaxies Survey Team,
NOAO, AURA, NSF
D. Hunter (Lowell Observatory), Z. Levay (STScI)
Mr. Mac’s Earth Science Classroom
The Milky Way
75,000 light-years
25 kpc = 25 kiloparsecs = 25,000 parsecs
8.5 kpc
(2/3 of the
way out)
“face-on”
 view
“edge-on” (looking from
the edge)
 view
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The Big Bang Theory: 10 billion to 20 billion years ago:
An expansion of space from a
single point..
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The Big Bang Theory: 10 billion to 20 billion years ago:
• Over time the universe has cooled, but is
still expanding today.
(What proof do we have?
Stay Tuned!) …
• After about 1 billion years,
the first stars and galaxies started to form….
The galaxies are expanding WITH space!!!
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The Big Bang Theory: 10 billion to 20 billion years ago:
Galaxies
are moving
with space
not through
it.
Think of
rasin
bread…..
There is no
center or
edges to
the
universe.
The are in
fixed
positions.
Getting
farther
apart from
one
another.
The Big Bang Theory: 10 billion to 20 billion years ago:
The “raisin bread” analogy
raisins  galaxies, dough  space
Mr. Mac’s Earth Science Classroom
The Big Bang Theory: 10 billion to 20 billion years ago:
The “raisin bread” analogy
raisins  galaxies, dough  space
Mr. Mac’s Earth Science Classroom
The Big Bang Theory: 10 billion to 20 billion years ago:
The “raisin bread” analogy
raisins  galaxies, dough  space
Note:
Note: galaxies
raisins are
arenot
notmoving
movingthrough
throughdough.
space.
Rather,
Rather, blobs
blobs of
of dough
space are
are expanding,
expanding, and
and
pushing
pushingthe
thegalaxies
raisins farther
fartherapart.
apart.
Mr. Mac’s Earth Science Classroom