Download (AU): Average distance from Earth to Sun

New Unit
Astronomy: Structure
of the Universe
42
Question of the Day
What is the evidence for the
Big Bang Theory?
Celestial Object
Any object outside Earth’s atmosphere
Universe
Everything that exists
Big Bang Theory
● Universe started as a small,
concentrated area of matter & energy
that exploded ~13 billion years ago.
● Expanding ever since.
In the beginning there was Energy…
 Which cooled into the first
matter:
 Hydrogen 75%
 Helium 25%
Evidence for the Big Bang
1. Background Radiation
Energy (microwaves) from
explosion found in all parts of
universe
2. Electromagnetic spectrum of
radiation from stars
Spectral Lines
Every element has a distinct pattern
Helium
Hydrogen
Neon
Oreos
2a. Doppler Effect –
• Wavelength shifting of
electromagnetic energy.
• Caused by motion between energy
source & observer (star and Earth).
2b. Red Shift
• Shift in spectrum
toward longer red
wavelengths
• Star is “RUNNING” AWAY
• Farther away, greater red shift.
• Almost all galaxies show red shift proof that universe is expanding.
Blue Shift
• Shift toward shorter blue wavelength
• Object is “BARRELING” TOWARD
Earth.
Doppler Effect
Red Shift = Object  Moving Away
Blue Shift = Object  Moving Toward
Questions
1. What are the 2 major pieces of
evidence to support the Big Bang
Theory?
2. If spectral lines are red-shifted,
is the object moving toward or
away from Earth?
Question of the Day
What is the structure of
the universe?
Warm Up
What evidence supports
the theory that the universe is
expanding?
http://htwins.net/scale/index.html
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Planet
Celestial body in orbit around
the Sun.
Solar System
A sun and its orbiting planets,
moons, and other celestial objects.
Galaxies
• 100+ billions of stars + gas and
dust, held together by gravity.
• 100+ billion galaxies.
Milky Way Galaxy
• Our spiral-shaped galaxy, with
200+ billion stars.
We’re 2/3rds distance from center
You are
here!
Universe
Everything that exists
Biggest
1. Universe
2. Galaxies
3. Solar Systems
Smallest
4. Planets
Distances in Space - Vast!
FYI: 240,000,000,000,000 (240 trillion)
miles to closest Star (other than Sun)
 Light-Year (LY): Distance traveled by
light in a year (FYI: 9.47 x 1012 km).
 Astronomical Unit (AU): Average
distance from Earth to Sun
(FYI: 149,597,870.691 km) = 1 AU.
 FYI: At 100 miles per hour (160 kph) it
would take over 100 years to go 1 AU.

Solar System is about 80 AU in diameter
1 AU
Earth
Nearest star is 4.4 light-years away
(7.866402828x1026AU)
Nearest galaxy is
50 million light-years away
(8,939094122x1027AU)
80-100,000 light-years
Each dot on
this screen is
an entire
GALAXY!!!
Order from biggest to smallest
Biggest
Galaxies
Planets
Solar Systems
Universe
Universe
Galaxies
Solar Systems
Planets
Smallest
Question of the Day
What is the structure of our
solar system?
Warm Up
What is LY? What is AU?
44
Solar System
• Held together by sun’s gravity.
• Formed 5 billion years ago.
1. Clumping of gas &
dust
2. Sun forms –
nuclear fusion.
3. More clumping –
planets form.
4. Planets separate by
density. Densest near
Sun.
5. Present solar system.
Formation
Parts of Solar System
1. Planet
• Celestial body in orbit around the Sun.
• 8 in our solar system: Mercury, Venus,
Earth, Mars, Jupiter, Saturn, Uranus,
Neptune
• Distance from the sun determines
characteristics (ESRT)
• Density generally decreases with
distance from the sun
2. Moon
• Body that orbits a
planet or an
asteroid, as those
objects orbit the
sun.
• Over 175 moons in
our solar system
3. Asteroids
• Small, solid, rocky or metallic
bodies that orbit the sun.
• Most are in a belt between Mars
and Jupiter
4. Comets
• Balls of ice & rock or metal that
turn to gas when heated by the sun
• Heating by sun forms a tail, which
is blown away from sun by solar
wind.
4. Comets
Particles and
radiation
from sun
pushes tail of
comet away.
Meteoroid - Very small solid fragment
that orbits the sun.
Most are size of a dime or grain of sand.
Meteor - Meteoroid that makes a streak
when it burns up in Earth’s atmosphere
Also called “shooting stars”.
Meteorite - Meteoroid that hits Earth,
forming an impact crater
Impact Event
Collision of comets, asteroids, meteoroids
or any other celestial body.
Meteor Crater, AZ
180 meters deep and 1.2 km in diameter
with an eroded rim standing 30-60 m high
Lunar Impact Crater
Terrestrial (Rocky) Planets
 Mercury,
Venus,
Earth, Mars
 Close to sun,
mostly solid
 Small diameters,
high densities,
few or no moons,
no rings, have
impact craters
Mercury
Ball of rock with iron core, -279°F to
800°F, many impact craters, no
atmosphere or water
Caloris Basin
Venus Runaway Greenhouse Gases
Thick clouds, acidic rain, poisonous
atmosphere, 890°F, many volcanoes
Earth - The Water Planet
Mars - The Red Planet
Thin atmosphere,
many dust storms,
impact craters,
presence of water in
ice caps, and ???
Jovian Planets - Gas Giants
• Jupiter, Saturn,
Uranus, Neptune
• Far from sun,
largely gaseous
• Large diameters,
low densities,
many moons, may
have small solid core,
no impact craters
Jupiter – The Largest Planet
The Great Red
Spot – a hurricane
that has lasted
300 years so far,
and is large
enough to fit
Earth inside!
Saturn
• Least dense
planet (< water).
• Rings made of ice
& rock (possibly
debris from a
destroyed moon)
Uranus
• Tilted almost completely on its
side. So during summer the sun
never sets, during winter the
sun never rises!
Neptune
• Mainly
hydrogen
atmosphere,
-225oC
Solar System Scavenger Hunt
In notebook, answer the following using ESRT:
1. Most massive object in solar system.
2. Most massive planet.
3. Least massive planet.
4. Densest planet.
5. Least dense planet.
6. Planet with diameter most similar to Earth.
7. Planet farthest from Sun.
8. Distance from Earth to our Moon (units!)
Answers
1. Sun
2. Jupiter
3. Mercury
4. Earth
5. Saturn
6. Venus
7. Neptune
8. .386 million km = 386,000 km
Question of the Day
How are stars
formed?
1. In your notebook,
categorize the 8 planets as either
Terrestrial or Jovian.
2. Name 2 characteristics of Terrestrial
planets and 2 of Jovian planets.
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Terrestrial
• Mercury, Venus,
Earth, Mars
• Close to the sun
and mostly solid
• Small diameters,
high densities, few
or no moons, no
rings, have impact
craters
Jovian
• Jupiter, Saturn,
Uranus, Neptune
• Far from sun &
largely gaseous
• Large diameters,
low densities, many
moons, may have
small solid core, no
impact craters
Star
• Large ball of gas held together by
gravity that produces tremendous
amounts of energy and shines.
• Sun - Our closest star.
Nebulas
• Gas & dust held
together by gravity.
• Birthplace of stars.
A Star is Born
Step 1 - Cloud Collapses
Nebula clouds of gas
& dust begin to
collapse due to
gravity.
Eagle Nebula
Step 2 - Fusion
• Cloud begins to
spin & heat up.
• Eventually, it
gets hot enough
for fusion
• Protostar is born.
Nuclear Fusion
Combination of smaller elements form
into larger elements. Some mass is
converted to energy.
Star Formation
• In core, 4 H atoms
fuse together to
make 1 new He
atom.
• This releases
huge amounts of
energy, and makes
the star expand.
Step 3 - Equilibrium
Opposite forces keep star in
balance:
1. Fusion in core
produces radiation
(light) that pushes
out.
2. Gravity pulls everything in.
Birth of a Star
1. Cloud
Collapses
2. Fusion
3. Equilibrium
Question
How is a star born?
1) Fusion, cloud collapses, equilibrium.
2) Equilibrium, cloud collapses, fusion.
3) Cloud collapses, fusion, equilibrium.
4) Get discovered, get an agent, get a
movie contract.
How Long Do Stars Live?
It depends on the mass of the star.
• LARGE stars live a short time, ~ 10 million
years. Think SUV.
• SMALL stars live a long time, hundreds of
billions of years. Think Prius or VW Beetle.
• Our SUN will live 10 billion years. It’s now
5 billion years old.
What happens next?
It depends on the mass
of the star.
Question of the Day
What is the life cycle
of stars?
Write down in notebook:
1. The 3 steps in a star’s formation
2. What determines how long a
star lives.
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1. Low-Mass Stars
Gas/Dust Star Red
(Main
Giant
Sequence)
White
Dwarf
Black
Dwarf
1. Low-Mass Stars
< 8 times our Sun’s mass.
● Fusion in core
begins to run out,
but continues in
outer shell.
● Expands to Red Giant.
White Dwarf
● In shell, outward
pressure from fusion
continues.
● Star explodes into
a planetary nebula
that leaves the core
of a White Dwarf.
Ring Nebula
White Dwarf
Burned-out core of a
planetary nebula.
• A sugar cube of White Dwarf
weighs several tons.
• Eventually cools down & becomes
a “dead star” - Black Dwarf.
• This is the destiny of our
Sun….billions of years from now.
2. High-Mass Stars
Gas/Dust Star
(Main
Sequence)
Neutron
Star
Super Supernova
Giant
Black
Hole
2. High-Mass Stars
> 8 times Sun’s mass.
● Higher temperatures
fuse heavier
elements, e.g., iron.
● Fusion in core
begins to run out, but continues
in outer shell.
● Expands to Super Giant.
Supernova
Collapse of iron
core triggers an
enormous
explosion into a
Supernova.
Supernova
remnant Crab
Nebula
Neutron Stars & Black Holes
Iron core of a high-mass star continues to
collapse and becomes a super-dense Neutron
Star. A teaspoon weighs 10 million tons!
BUT iron core of a very-high-mass star
collapses further and becomes … a Black Hole.
1. Low-Mass Stars
Gas/Dust Star Red
(Main
Giant
Sequence)
White
Dwarf
Black
Dwarf
2. High-Mass Stars
Gas/Dust Star
(Main
Sequence)
Neutron
Star
Super Supernova
Giant
Black
Hole
Question
A low-mass Red Giant star
becomes a
1) White Dwarf
2) Black Hole
3) Neutron Star
4) Supernova
Question
The life cycle of a star depends
on the star’s
1) Color
2) Shape
3) Mass
4) Movie agent
Organize into a flow chart:
Black dwarf
Supernova
White dwarf
Neutron star
Main sequence
Nebula
Black hole
Red giant
Super giant
___________
Black dwarf, Supernova
White dwarf, Neutron star
______________
Main sequence, Nebula
Black hole, Red giant
______________
________________
_______________
Super giant
________________
_______________
_________________
________________
Nebula
Main Sequence
Red giant
Super giant
White dwarf
supernova
Black dwarf
Black hole
Neutron star
You are made of
stardust!
Live Long and Prosper …
Spirograph
Nebula
Cat’s Eye
Nebula
Boomerang
Nebula
Question of the Day
How are stars classified?
Warm Up:
Categorize Giants, Supergiants, Main Sequenc
& White Dwarfs under these stages:
Early Stage
Intermediate Stage Late Stage
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Star Classification

Luminosity: Actual brightness.
Depends on size & temperature.
 Bigger
is brighter
 Hotter is brighter
Absolute Magnitude: Actual brightness
if all stars same distance from Earth.
 Apparent Magnitude: How bright a star
appears to be to an observer on Earth.
- Depends on distance. Closer = brighter

Characteristics of Stars (ESRT)

Groups stars by luminosity and
temperature (HR Diagram)
Y-Scale: Luminosity – Brightness
compared to sun.
 Sun = 1
 < 1 = Dimmer than Sun
 > 1 = Brighter
BEWARE: The Scary Scale!!!!

X-Scale: Temperature
DANGER: IT’S BACKWARDS!
10,000
L
U
M
I
N
O
S
I
T
Y
A
B
C
D
1,000
100
10
30,000
20,000
10,000
Temperature (K)