Cosmology,
Galaxies, and
Stars
OUR VISIBLE UNIVERSE
Cosmology

Cosmology is the study of the universe; its nature, origin and
evolution.


General Relativity is the mathematical basis of cosmology from
which equations were derived that described both the energy
and matter content of the universe.
Outward Expansion vs. Inward Collapse:

The Universe struggles with the force of its outward expansion
(helped most likely by dark energy) and the inward force of
gravity; ultimately the strongest force will win and determine
the future of our universe.

The rate of expansion can and is calculated and this can in
turn date the age of the universe.

Mathematical equations and models
support the Big Bang Theory.

Before the Big Bang, there was an
“emptiness” called singularity.

The expansion is theorized to have
begun with a single primordial
(“beginning) atom.

Expansion shows that the universe must
have had a beginning.

The beginning was a rapid expansion
rather than an explosion and there was
no sound or bang.

The young universe was extremely hot
but cooled with expansion.

About 750,000 years after initial
expansion, the first radiation appeared.
The Big Bang-13.7 billion years ago
Evidence to Support the Big Bang Theory
Hubble’s Law

It is the observation that the further away
the object, usually a galaxy, the faster is
moving away.

The observation supports the Big Bang
Theory.

However, the increased speed of further
objects it not yet understood, could be
dark energy.
Cosmic Background
radiation

Shortly after the initial
expansion, the universe filled
with electromagnetic
energy.

With the expansion, the
energy gained longer
wavelengths.

The cosmic background
radiation was first observed in
Holmdel NJ with a radio
telescope.

This energy was observed
being emitted from every
object in space.
Electromagnetic Spectrum
• The larger the radiation or vibrations, the least dangerous but these
waves travel further into space- ex. Radio
• The smaller the radiation or vibrations, the more intense and
dangerous- ex. Gamma rays

Spectral Lines are created by
the different chemicals
burned within the star.

Each element has a specific
“fingerprint” or alignment of
spectral lines.

The spectra can help us
determine what the stars are
made of, as well as the
motion of the stars.

Redshift- it is the shift of
spectral lines toward the red
(longer wavelength) end of
the spectrum

The longer wavelength
demonstrates that the object
is moving away.

Redshift supports the Big
Bang Theory
Star Spectra

Redshift is being demonstrated in the
above spectral lines.

The Supercluster is moving further
and faster away than the sun.
Possible outcomes for the future:
Open Universe
Flat Universe
•This theory states that
everything in the
universe will continue
to move outward and
away with continual
expansion infinitely.
•Eventually, all stars
would burn out
leaving our universe
with empty darkness.
A flat universe results
if the expansion
slows to a halt in an
infinite amount of
time but never
contracts.
Expansion occurs so
slow that it appears
to have stopped.
Closed Universe:
The Big Crunch
•This theory supports the
idea that eventually that
outward expansion from
the initial Big Bang will wear.
•At this point, the force of
gravity will begin to pull
everything back together
again.
•Then, another Big Bang will
occur!
Dark Matter and Dark Energy

Cosmologists estimate that the
universe is 21% matter (stars,
planets…) and 78% dark energy
and luminous energy.

This is a “force” that is believed
to be like an anti-gravitational
force that could be the cause
of the dramatic expansion of
the Universe.

Dark matter and dark energy
are still undefined today.

We believe dark matter consists
of subatomic particles, smaller
than protons and neutrons!

Scientists recognize the effects
of dark energy, but they still do
not know exactly what it is.
Types of Galaxies:
Galaxy- a cluster of billions and trillions of
stars bound together by gravity
Elliptical Galaxyround and flattened
ovals
(This is the most
common type of
galaxy)
Irregular Galaxysmaller galaxies
with no distinct
shape.
Spiral GalaxyGalaxies with
spiraling arms
that rotate
around a central
bulge of massive
substance in the
center.
Barred GalaxyA flattened disk
with two distinct
rotating arms
The Hubble Telescope Finding:
The Hubble Telescope found the oldest thing in the Universe. The galaxy
is 13.2-billion years old, we are technically seeing this galaxy when it
was very young, but its light is only reaching Earth now
.
Groups and Clusters of Galaxies
Most galaxies are located in groups rather than spread out.
Local Group:
Large Clusters:
Superclusters:
• The Milky Way belongs to • There are clusters
• These gigantic
a small group of galaxies
larger than the
formations are hundreds
called the Local Group.
local group,
of millions of light-years
• It is 2 million ly in diameter anywhere from 5in size.
• Has 40 members
30 million ly.
• The Milky Way and
Andromeda are the
largest.
Our Local
Group
A distant
Supercluster
The Milky Way
Formation

The Milky Way began forming around 13
billion years ago, give or take 800 million
years.

The halo, or central disk, contains extremely
old stars, suggesting that the halo formed
first.

The galaxy began as a spherical cloud.

The cloud eventually collapsed under its
own gravity.

The halo also contains the super giant stars
which burn heavier elements.

There is also a galactic black hole that is
larger than our solar system.
Galactic Black holes- weighing a few billion times
the mass of the sun, most galaxies have a
supermassive Black holes in their center. (ours is
slightly smaller than our solar system!)
•
Our Galaxy:
The Milky Way
•The
center is over 28,000
light years away. Which
means it takes 28,000 years
for the light of the stars in
the center to travel through
space and be seen by our
planet!!!
•
Sun orbital
speed around
the center is
220km/s,
orbital period
is 240 million
years.
The sun will
complete 20
revolutions
around center
in its lifetime.
•A
light year is the distance
light travels in one year,
moving at 186,000
miles/second.
•The
direction towards the
center is toward the
constellation Sagittarius.
galaxy contains over
100 billion stars!
Sun
•Our
Most stars in the Milky Way are 207,000 AU (AU=
•The Sun is located on the
distance between sun and earth, 90 million miles) apart,
Orion Arm
but in the center they are only 1000Au apart!!!
Hertzsprung-Russel Diagram
• The H-R Diagram, is a
diagram that shows the
relationship between
temperature and
brightness.
• As a star becomes hotter, it
becomes brighter.
• Main sequence is the
pattern of the average star.
• The sun is located within the
Main Sequence.
• The stranger exceptions to
this pattern are located
outside of the main
sequence.
H-R Diagram Animation
Life Cycle of a Star
White dwarf will
eventually stop
nuclear fusion
and become a
black dwarf”Dead Star”
Medium
Star
Gravity condenses the
star to shrink
(Where protostars are
formed)
Giant Star
Nebula- the birth of a star
Orion Nebula
Lagoon Nebula
Horsehead Nebula
A Nebula is a cloud of cosmic gas and
dust where stars are formed.
•The gases of these nebulas are mostly
hydrogen and helium.
• These are the two gases that make
up all stars!
•Gravity begins to pull the gases inward
during the birth of a star.
•Then, with gravity, the density of the
gases increases which causes the
pressure and temperature to increase,
until the star finally stabilizes.
•A star can exist anywhere from 1
Million to 30 Billion years! (depending
on size)
•Our Sun has around 5 Billion years
remaining. It is predicted to only exist
for 10 Billion total years.
Young Stars
Protostar:
•After the nebula, the cloud collapses in
on its own gravity.
•As the cloud contacts, it rotation forces
form it into a disk with a hot, condensed
object called a protostar.
•Once the protostar becomes hot
enough, nuclear fusion will begin.
•Nuclear fusion converts hydrogen to
helium in the core of a star. Once this
begins, the star becomes more stable
between the outward force of gravity
and the inward force of gravity.
Medium Star:


Temperature= 6000°C
Color = yellow/orange

Example= Our Sun (closest star
is proxima centauri)

Exist for up to 10 billion years
Giant and Supergiant Stars
Giant Stars
•When a star runs hydrogen in the core
causing the star to expand.
•The core now has the ability to make
carbon in the core.
•Color= Red or Blue
•Temperature= 4500°C
•Size= 10 x time the size of the Sun
Red Super Giant Stars
•
Under goes more reaction phases and
thus produces many different elements in
its core.
•Color= Red
•Temperature= 3000°C
•Size= 1000 x the size of the Sun!!
As size increases, the temperature decreases because the heat of nuclear
fusion is spread out over such an enormous volume!
Supernova to a
Planetary Nebula
•A
star that begins with mass
between 8-20 times the Sun’s
mass will end up with a core
that is too massive to be
stable.
•The star’s core then produces
iron and no energy which
causes the core to violently
collapse.
•Then entire outer portion of
the star is blown off in a
massive explosion, supernova.
•This explosion leaves behind
heavier elements which can
condense to planetary
nebulas, such as our own solar
system.
•A distant supernova
explosion might be brighter
than the galaxy in which it is
found.
Computer Animation
Actual
Supernova70 mill light
years away
and occurred
millions of
years ago!
White and Black Dwarf Stars
White Dwarf Stars:
•Color
= White
•Temperature=
•Size=
Texas
15,000°C
Average around the size of
Black Dwarf or “Dead Stars”
•These
are stars that have burned
out and nuclear fusion is no longer
occurring, therefore these stars are
creating no energy.
•Pressure
causes these stars to
become extremely dense, similar
to squeezing an aircraft carrier
into a glass jar!
Both images are computer
animations. Black Dwarfs do not
give off any light to be seen.
Neutron Star
Color: Blue
Temperature: 35,000°C
Size: A little larger than New York City (5-10
Miles)
•The Neutron Star is extremely dense and
small.
•The neutron star forms when are a
supergiant star’s protons and electrons
combine to form neutrons.
•The creates pressure that halts the collapse
of the core.
•These neutrons stars can have 1.5 to 3 times
more mass that the sun.
•10,000,000,000,000,000 g/cm3
Pulsar
•
Some neutron stars are unique
in the have a pulsating pattern
of light.
•
This causing them to emit their
magnetic fields into cones or
spinning beams of lights.
Black holes
•
Some stars are too massive to form
neutron stars.
•
The pressure can not support the star’s
core.
•
Usually happens to stars that are at least
20 time our sun.
•
The star than collapses compacting the
matter into a smaller volume.
•
The remaining, extremely , small and
dense object becomes a black hole.
•
The gravity of these objects is so greater
that not even light can escape.
•
The fundamental descriptions of black
holes are based on equations in the
theory of general relativity developed by
the German-born physicist Albert Einstein.
The theory was published in 1916.
•
The EVENT HORIZON is the area of no
return, where an object is within the
gravitational pull of a black hole and
there is no escape.
These are computer animations- true black
holes cannot be seen because light cannot
reflect off them to create a shape.
This is an actual black hole in the center of our galaxy.
The black hole cannot be seen but can be observed by
what it is “eating” as the stars simply disappear under its
enormous gravity.
Nebular Theory:
Creation of Our Solar System

The Nebular Theory states that gaseous
clouds—nebulae(most likely the
remnants of a massive supernova),
slowly rotate, gradually collapse and
flatten due to gravity and eventually
form stars and planets.

Our solar system was formed 4.568 billion
years ago when a small part of a giant
cloud collapsed inward on its own
gravity.

First the protostar, our young sun, cloud
(a nebular cloud) contracted and
cooled, flattening and shedding rings of
material in the process which later
collapsed to form the Planetisimals.
A massive nebula remained for a large
supernova.
Cloud began to rotate quickly and flatten
Very hot proto-sun began to form
Our sun and Planetisimals formed.

Matter Accretion or “snow-balled into
today’s planets.