Galaxies and the Universe
Spectra of Science
Amole
2013
The Hierarchy
World
Universe
Continent
Galaxy
Country
Stars
State
Solar
System
City
Planet
The Universe
• The sum of all space, matter, and energy that
exists, has existed, or will exist
• There is only one
• You are part of it too!
• We see it as it was in the past
• Contains many other galaxies
• Most of it is empty space
The Hubble Telescope
• A reflecting telescope that was placed into orbit in 1990
• Sends images and measurements back to Earth
electronically
• A deep image of an “empty”
portion of the sky reveals that
the universe is filled with
galaxies
• The light we see from the
most distant galaxies has
traveled approximately 10 billion years to reach us
Galaxies
Fun Fact:
If you of
counted
1,000
galaxies
• A collection
stars, dust,
and gas
bound a
night,
it would take 275, 000
together
by gravity
years!
• We live in the Milky Way
galaxy
• There may be more than 100 billion galaxies
• Not spread out evenly
Funthrough
Fact: space; exist in
clustersThe Milky Way is part of a
– Clusters
can join
and form
superclusters
cluster
called
the
Local Group.
The Milky Way Galaxy
Galaxy Types
Spiral
have arms of
stars, gas , and
dust that curve
away from the
center of the
galaxy in a spiral
pattern
Ex. – Milky Way
Elliptical
shaped like
spheres or
eggs; have
almost no dust
or gas between
stars; contain
old stars
Irregular
faint galaxies
without a
definite shape;
smaller than the
other types of
galaxies; contain
fewer stars
The Big Bang Theory
Occurred 10-20 billion years ago
Before there
was nothing Alert:
Misconception
No space;
No time this theory as
Describing
Out of
the
nothingness
“Big Bang”
came
is aanmisnomer
explosion of
energy
in all directions
because
there really was not
• This an
energy
gave rise
to all
the matter
explosion,
just
a release
of we
know today
energy
• Thought to have expanded within a
second from something the size of a spec
of dust to the size of our solar system
•
•
•
•
The Big Bang
• After 3 minutes, protons and neutrons began
to fuse to form the nuclei of hydrogen and
helium atoms
• About 300,000 years later, temperatures were
cool enough for complete hydrogen and
helium atoms to form
• Photons escaped from matter about the same
time, and light existed for the first time
The Big Bang
• After under a billion years the first stars form
– They live and die slowly creating heavier elements
• Galaxies and clusters also begin to slowly follow
The Evidence
• Edwin Hubble
determined that other
galaxies exist, besides
the Milky Way
• He observed that
galaxies were moving
away from each other
– Hubble Law – the
farther away a galaxy
is, the faster it is
moving away from us;
supports the Big Bang
Theory
The Evidence
• Hubble found spectral lines shifted
towards red
The Evidence
• Explained by the Doppler Effect
– Objects that are moving away from us emit
longer wavelengths
– Toward the red end of the spectrum
The Evidence
• Arno Penzias &
Robert Wilson
accidentally
detected faint
radiation on a radio
telescope in 1965
• Determined that
the radiation was
leftover thermal
energy from the
“big bang”
The Fate of the Universe
1. The universe will keep expanding
forever
2. The expansion
of will
the universe
The fate
depend will
gradually slowon
down,
and approach a
mass!
limit in space
3. The universe will stop expanding and
start to fall back in on itself
The Fate of the Universe
1.
Too much = gravity
will cause everything
to collapse on itself
2.
Too little = not
enough gravity to
stop expansion
3.
Just right = it will
slow down, but never
really stop
Einstein’s Theory of Relativity
• Mass curves space
– Think about how a mattress reacts when you
sit on it
• During a solar eclipse scientists noticed
stars were in different positions than
expected
Interstellar Matter
• The gas and dust located between stars
and galaxies
Quasar
• The most distant and radiant objects in
space
• Discovered by the radio waves that
they emit
• May be infant galaxies
• May have huge central black holes
Dark Matter
• Highly debated
• Scientists have evidence that there may
be more matter than just that that is
visible
• As much as 90% of universe may be dark
matter
• Could be planets, black holes, or brown
dwarfs (stars that never start fusion)
Astronomical Unit (AU)
• unit of distance equal to the average spacing
between the Earth and the Sun
• equal to about 150 million kilometers (93
million miles)
• light takes about eight minutes to cover this
distance
150 million km
(93 million mi.)
The Earth
animation is
not rotating
in the
correct
direction;
it should be
rotating
from west to
east
Light Year
• the distance that light travels in one year in a
vacuum, which is about 9.5 trillion kilometers
(6 trillion miles)
– The Milky Way Galaxy is about 100,000 light years
in diameter
• the speed at which light travels this distance
is about 300,000 km/sec (186,000 mi/sec)
Fun Fact:
The second closest star to
the Earth is a little over four
light years away.
Parsec
• unit of distance equal to about 3.26
light years (or 206,265 AU)
Parallax
• the apparent shift in position of an
object when viewed from different
locations
• used by astronomers to measure
distance
Try This:
Focus on the star to the left. Open
and close your eyes in an
alternating manner. What do you
notice about the star’s position?