• “We are all connected; To each other,
biologically. To the earth, chemically. To
the rest of the universe atomically.”
~ Neil deGrasse Tyson
Stars & Galaxies
If you could travel at the speed of
light (186,000 miles per second) it
would take 100,000 years to cross
our galaxy
Even on the clearest night, the human eye can only see
about 3,000 stars. There are an estimated
100,000,000,000 in our galaxy alone!
Stars
Constellations
• Patterns of stars representing
mythological characters,
animals, or familiar objects.
• Most constellations come from
the Greeks.
• The stars in a constellation may
appear close, however each star
can be millions of light-years
away from each other.
• There are 88 constellations used
to divide the night sky.
Vega was the
north star around
12,000 BC and will
be so again
around AD 13,727
Circumpolar Constellations
 Constellations that appear to circle around the
North Star, Polaris.
 These constellations are visible all year and
never go below the horizon.
Ursa Major, Ursa Minor, Draco, Cepheus,
Cassiopeia, Camelopardalis
Zodiac Constellations
 12 constellations that line up on the
ecliptic with the planets.
 For about a month, one of these
constellations is hidden behind the Sun.
Vega is rotating rapidly with a
velocity of 274 km/s at the
equator.
Absolute & Apparent Magnitude
• Absolute Magnitude refers to the measure of light
that a star actually gives off.
• Apparent Magnitude refers to the amount of light
the Earth receives from the star.
The largest recorded starquake
occurred on the neutron star
SGR 1806-20. It was a 22.7 on
the Richter scale. The quake
released enough gamma
radiation that had it been within
10 ly of Earth (it is 50,000 ly
away) it would likely have
caused a mass extinction.
Measurement in Space
• Parallax- the apparent shift in the position of an
object when viewed from two different positions.
» The closer the object is to the observer, the greater
the parallax.
Light-years- the distance light travels in one year
(9.5 trillion km in one year.)
»Proxima Centauri is the closest star to the Sun
at 4.3 ly.
Properties of Stars
• Temperature- determined by the star’s “surface”
color.
From hottest to coolest:
Blue
Blue-white
White
Yellow-white
Yellow
Red-orange
Red
Composition
 Observed from the light given off by the star
using a spectroscope.
 A prism in the spectroscope divides the light
into its component colors.
 The colors present/absent in the spectrum
indicate the elements present in the star. Similar
to a fingerprint.
The telescope on Mount Palomar,
California, can see a distance of
7,038,835,200,000,000,000,000 miles.
Hydrogen
Helium
Carbon
The Sun
If a pinhead-size piece of the Sun were
placed on Earth, one would have to stand
as far as 145 kilometers (90 miles) away
to be safe.
The Sun’s Layers
• The Sun is a giant ball of gas/plasma.
Core- hydrogen is fused into helium giving off
massive amounts of energy (Nuclear Fusion.)
above 15 million K.
Radiative/Convection Zones- area through which
the energy travels outwards.
Atmosphere- outermost region of the Sun
Gravity on the sun is 30 times stronger. 70 lbs
on Earth would be 1 ton on the sun
The sun is….
109 Earths across
93 million miles away
176 years away at 60 mph
It would take 1,300,000 Earths to fill
the sun.
You could string 340 Earths around
the equator of the Sun
Temperatures on the sun range from
7000 to 27,000,000° F
The Sun’s Atmosphere
Photosphere- lowest layer of the Sun’s
atmosphere.
 This is considered the “surface” because this is
the part we see from Earth.
 Sun’s photosphere is yellow at 6000K
 Chromosphere- layer above the photosphere.
 Corona- highest & largest layer.
 Charged particles reach 2 million K
The Earth orbits the sun at an average
speed of 107,220 kms per hour.
If the sun were the size of a dot on an
ordinary-sized letter 'i', then the nearest star
would be 10 miles away.
1. Core
2. Radiative Zone
3. Convection Zone
4. Photosphere
5. Sunspot
6. Chromosphere
7. Corona
Mass of the sun is 330,000 bigger than Earth.
Sol has 600 times more mass than all the
planets put together!
The light hitting the earth right now is 30 thousand years old. The energy in the sunlight we
see today started out in the core of the Sun 30,000 years ago – it spent most of this time
passing through the dense atoms that make the sun and just 8 minutes to reach us once it
had left the Sun! The temperature at the core of the sun is 13,600,000 kelvins. All of the
energy produced by fusion in the core must travel through many successive layers to the
solar photosphere before it escapes into space as sunlight or kinetic energy of particles.
“Surface” Features
Sunspots- cooler dark areas
 Appear & disappear regularly
 Magnetic storms
Prominences- huge, arching columns of gas.
Flares- violent eruptions of particles near
sunspots.
Solar Winds- particles ejected from the Sun’s
corona.
 Bounce of the Earth’s atmosphere causing the
auroras.
There is a current scientific hypothesis that the sun possibly has a companion which is currently
about 1-1.5 light years away. It is believed that it has an elliptical orbit which, every 26 million years,
sends matter towards the earth causing mass Extinction events. The star is predicted to be most
likely a red or brown dwarf and has been named Nemesis or “Death Star”.
Sunspots
The Sun loses up to a
billion kilograms a second
due to solar winds
Scientists haven’t been able to
work out how Stradivari
(famous violin maker) made
his violins but they think it is
due to the wood he used.
From 1500s to 1800s the earth
underwent a mini ice age due
to volcanic activity and
decreased solar activity. As a
result of the cooling, the trees
he used were particularly hard
(due to slow growth). If he
hadn’t had those trees to work
with, his violins might now
have been so highly prized.
Prominences
Solar Flares
The Sun – An Average Star
• Middle-aged star, average absolute magnitude, &
average temperature.
Multiple star systems
 The Sun is NOT part of a multiple star system
unlike most stars.
2 stars is a binary system, 3 stars is a triple-star
system (Alpha Centauri system)
Star Clusters
Stars that are so close that they move together as
a unit.
Classifying Stars
III. Evolution ofDiagram
Stars
Hetrzsprung-Russell
• Ejnar Hertzsprung & Henry
Russell independently charted
the relationship between a
star’s temperature to its
absolute magnitude.
• It showed that the hotter stars
are also the brightest stars,
with a few exceptions.
• 90% of all stars fit into a
diagonal line in the middle of
the graph (Main Sequence.)
The Main Sequence
 Contains hot, blue giant stars that are very bright
to cooler, red dwarf stars that are very dim.
 Yellow, medium sized stars are in the middle of
the Main Sequence like the Sun.
Dwarfs, Giants, & Supergiants
 10% of stars are not main sequence.
 Stars that are very hot (white-blue,) but are dim are
called the White Dwarfs.
 Stars that are cooler (red-orange,) but are very
large and bright are called the Red Giants.
 The biggest, coolest, & brightest stars are the Red
Supergiants.
The Solar System
Medium to Red Gian
The star "Lucy" in
constellation Centaurus
is actually a huge
cosmic diamond of 10
billion trillion trillion
carats.
The star Antares is 60,000 times larger than our sun. If
our sun were the size of softball, the star Antares
would be as large as a house.
Giants to Supergiants
Nuclear Fusion
• Four hydrogen nuclei combine to create
one helium nucleus.
• The mass of one helium nucleus is much
less than 4 hydrogen nuclei, so some of the
mass is lost in the reaction.
•The lost mass is converted into large
amounts of energy in the form of light.
(Temps in the core exceed 15 million K)
Evolution of Stars (Cosmology)
Step 1. Nebula-stars start out as clouds of dust &
gas. Gravity pulls it together.
Step 2. Protostar-the mass of gas gets bigger &
bigger eventually heating up to 10 million K
causing fusion.
Step 3. Main Sequence- when the pressure formed
by the heat balances the attraction due to gravity it
reaches equilibrium.
Nebula
Protostar
Main
Sequence
Pillars of Creation refers to a
photograph taken by the Hubble
Telescope of elephant trunks of
interstellar gas and dust in the
Eagle Nebula, some 7,000 ly from
Earth
The Pillars of Creation
no longer exist. In
2007, astronomers
announced that they
were destroyed about
6,000 years ago by the
shock wave from a
supernova. Because
of the limited speed of
light , the shock wave's
approach to the pillars
can currently be seen
from Earth, but their
actual destruction will
not be visible for a
1000 years.
Gomez’s Hamburger is a young
star surrounded by a
protoplanetary disk about 900 lightyears away.
Step 4. If it has:
Small Mass
» Red dwarf stars with eventually run
out of hydrogen and will collapse
into a hot, White Dwarf.
Medium Mass
» Yellow or white stars that will run
out H causing the atmosphere to
expand and cool into a Red Giant.
» He will fuse into a carbon.
» It will eventually collapse into a
White Dwarf
Because the Sun is hottest at its center, it will
use up the hydrogen at its center first. Then,
over the next few hundred million years, it will
fuse hydrogen in a spherical shell around the
center of the star.
In this phase, the Sun will turn into a red giant.
The center of the Sun will not be hot enough to
fuse helium, and will be surrounded by a layer
where there is hydrogen still burning. After a
few hundred million years, the helium core will
grow large enough that the temperature and
pressure near its core will be hot enough to
start burning helium.
List of things that fuse in a star. All but the fusion of iron is
exothermic.
Large Mass Stars
» Blue stars will expand into Red Giants when they
run out of hydrogen and helium fuses into carbon.
» Carbon will then fuse into heavier & heavier
elements causing the star to expand further into a
Red Supergiant.
» When iron is formed from fusion, iron can’t be
fused so the star collapses violently in a
Supernova.
SN 2006gy was an extremely energetic supernova , sometimes called a
hypernova, that was discovered on September 18, 2006. SN 2006gy
occurred in a distant galaxy, approximately 238 million light years away.
Therefore, the event occurred about 238 million years ago. Preliminary
indications are that it was around 150 solar masses.
»Depending on the mass of the core, one of the
following will occur:
Neutron Star- smaller cores will produce a dense
core of neutrons about 20km in diameter.
compression from the star's gravity will be so great the
protons fuse with the electrons to form neutrons
Neutron stars are so dense, that a
soup can full of neutron star material
would have more mass than the
At 12.5 miles (20
Moon.
kilometers)—neutron
stars boast nearly 1.5
times the mass of our
There is a neutron star that spins
sun, and are thus
on its axis at 1,122 times every
incredibly dense. Just
second.
a sugar cube of
neutron star matter
would weigh about
one hundred million
tons on Earth.
4 to 8 times the size the sun supernovae. This blows a star's
outer layers into space, the core
remains—but it no longer produces
nuclear fusion. With no outward
pressure from fusion to
counterbalance gravity's inward pull,
the star condenses and collapses in
upon itself.
A neutron star is the strongest
magnet in the universe.
Black Hole- larger cores will
collapse to a super dense
point. The gravity near this
mass is so strong nothing can
escape from it, not even light.
Locate using X-rays.
» Event Horizon is the area
where nothing can escape.
there is a super massive black hole at the
center of the Milky Way galaxy. It weighs
about 4 million solar masses (it’s over
30,000 light years away.)
Black holes can’t suck up all of the
matter in the Universe. Each black
hole has its own event horizon,
much like the gravitational field of a
planet. If matter is not in that
horizon it will never get sucked into
the black hole.
Centaurus A is the nearest example of an active galactic
nucleus (AGN), located only 10 million light years from us.
The black hole at the center of this galaxy is thought to
be around 60 million times the mass of our Sun; material
around it gets shot off in the form of huge jets which travel
at nearly the speed of light and are easily visible in
this Chandra x-ray image. Many of the small dots
surrounding the central AGN are thought to be
microquasars, smaller black holes which shoot off jets of
their own as they rip material from companion stars.
Galaxies & the Universe
The cosmos contains approximately
50,000,000,000 galaxies.
Galaxies
• Large group of stars, gas, and dust held together
by gravity.
-Spiral Galaxies- galaxies with spiral arms that wind
outward from the center. They can be normal or
barred.
When you look at the Andromeda galaxy (which is 2.3 million light years away), the
light you are seeing took 2.3 million years to reach you. Thus you are seeing the
galaxy as it was 2.3 million years ago.
Tadpole
Galaxy
Time is relative
The closer an object gets to the
speed of light, that object
actually experiences time at a
significantly slower rate. If the
you were traveling safely at
close to the speed of light to the
center of our galaxy from Earth,
it would take 25,000 years of
Earth time. For the you,
however, the trip would probably
only take 10 years.
It is now thought that
almost all galaxies
contain gigantic
black holes in their
centers, millions or
even billions of times
more massive than
the Sun
-Elliptical Galaxies- common
type of galaxy that are oval or
egg shaped.
-Irregular Galaxies- galaxies
that have no distinct shape.
cosmic year is the
amount of time it takes
the Sun to revolve
around the center of
the Milky Way, about
225 million years.
Hubble Deep Field
You are looking
back into the past by
13 billion years in
this picture
Each spot of light isn’t
a star….
It’s an entire galaxy.
About 1500 of them
with ~ 100 billion stars
per galaxy
how arrogant would it
be to think we are the
only life in the
universe.
Deep Field Video
The Milky Way
• Spiral galaxy that is about 100,000 ly across.
• Out solar system is located about half-way out on
one of the spiral arms.
• Like many galaxies, the Milky Way has a super
massive Black Hole at its core.
On average, every star in the Milky Way is accompanied by 1.6 planets. That’s at least 100
billion planets
We
moving through
space
at the
of 530km a second
Sunare
is 23,000
light-years
from
it'srate
center
Origin of the Universe
• Steady State Theory- the Universe has
always been the same as it is today.
• Oscillating Model- the Universe expands
and contacts in a cycle.
• Big Bang Theory- the Universe started with
a bang and has expanded ever since.
Expansion of the Universe
•Doppler Shift- the changing of the wavelength of
sound or light as an object gets closer or further
away.
•Red Shift- as a star or galaxy gets further away from
the Earth, its light will expand (stretch) producing a
longer wavelength (red) in the spectroscope.
Blue Shift-as a star or
galaxy gets closer to the
Earth, its light will get
compressed (squeezed)
producing a shorter
wavelength (blue) in the
spectroscope.
» Most galaxies show red shift, therefore the
Universe is expanding.
The Big Bang Theory
• All energy & matter was created in an instant
with an initial explosion.
• The matter rapidly expanded throughout space
in a swirling, dense mass.
• Matter began to collect into clumps. As matter
cooled, hydrogen & helium gases formed.
• Eventually the first stars will form followed by
galaxies, etc while still expanding.
Quasars are extremely distant objects in our known
universe. They are the furthest objects away from our
galaxy that can be seen. Quasars are extremely bright
masses of energy and light. The name quasar is
actually short for quasi-stellar radio source or quasistellar object.
A quasar is believed to be a supermassive black
hole surrounded by an accretion disk.
Evidence of a black hole
When we look at quasars which
are 10-15 billion light years away,
we are looking 10-15 billion years
into the past.