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Astronomy
‘A Guide to the Universe’
When you look up at the night
sky, you are looking into the
past!
Astronomy
• Astronomy is the study of the universe. It
is the study of planets, satellites, stars,
and galaxies and everything related to
them.
• Since we cannot travel to most of these
places, much of our knowledge comes
from observation, space probes, and manmade satellites sent up to collect data as
well as from telescopes.
How it All Began
• Scientists hypothesize that
approximately 13.7 billion years ago,
a rapid expansion created the
universe, producing energy and all the
material from which the stars, planets,
satellites, and all other objects
formed. (ATOMS & ELEMENTS)
• This theory is known as ‘The Big
Bang Theory’
The Expanding Universe
• Since the Big Bang, the size of the universe
has been increasing rapidly. The universe is
billions of times larger now than it was early in
history.
• Edwin Hubble first discovered that most other
galaxies are moving away from us.
– Hubble’s Law states that the farther a galaxy is
from us, the faster it is moving away from us.
• About 200 million years after the Big Bang, the
first stars and galaxies formed.
The Universe
• Astronomers define the universe as all
space and everything in it.
• The universe is enormous, almost beyond
imagination.
• Since the numbers astronomers use are often
very large or very small, they frequently use
scientific notation to describe sizes and
distances in the universe.
Galaxies
•
The word ‘galaxy’ comes from a Greek word
meaning milk.
•
A galaxy is a large group of stars, gas, and dust
held together by gravity.
•
There are 3 major types of galaxies:
1. Spiral Galaxy
2. Elliptical Galaxy
3. Irregular Galaxy
Spiral Galaxies
• Spiral galaxies have
arms that wind outward
from the center.
• Spiral galaxies can be
normal or barred.
• Arms in a normal spiral
start close to the center
of the galaxy.
Barred Spiral
• Barred spirals have
spiral arms extending
from a large bar of
stars and gas that
passes through the
center of the galaxy
Elliptical Galaxy
• A common type of
galaxy.
• These galaxies are
shaped like large, 3D
ellipses.
• Many are football
shaped, but others
are round.
Irregular Galaxy
• This category includes
most of the galaxies
that don’t fit into any
other.
• They have many
different shapes.
• They are smaller than
the other 2 types of
galaxies.
The Milky Way Galaxy
• Our solar system is located in a spiral galaxy
called ‘The Milky Way.’
• The center of the galaxy is about 25,000 lightyears away, but it is hidden from view by large
clouds of dust and gas.
• The Milky Way might contain 1 trillion stars.
• It takes the Sun 225 million years to orbit the
center of the Milky Way.
• Like many other galaxies, the Milky Way has a
supermassive black hole at its center.
• Seyfert's
Sextet is an
example of a
galaxy group.
Stars
• When ancient observers around the world
looked up at the night sky, they imagined
that groups of stars formed pictures of
animals or people. Today, we call these
imaginary patterns of stars, created by
man, constellations.
Characteristics of Stars
• Characteristics used to classify stars
include:
– Color
– Temperature
– Size
– Composition
– Brightness
Which stars are the hottest?
Spectroscopy – Continuous
Spectrum
Continuous Spectrum
Spectroscopy – Absorption
Spectrum
Hydrogen Absorption Spectrum
Spectroscopy of the Sun
Hydrogen, Helium, Neon, Silicon, Carbon, Oxygen, Nitrogen, Magnesium, Iron
Stars and the Periodic Table
• Elements heavier than lithium are all created in
stars. During the late stages of stellar
evolution, massive stars can burn helium into
carbon, oxygen, silicon, sulfur, and iron.
• Elements heavier than iron are produced in
two ways: in the outer envelopes of supergiant stars and in the explosion of a
supernova.
• All carbon-based life on Earth is literally
composed of stardust. (That’s us!)
Types of Stars/Size
• Main sequence stars (Young)
• Giants and Supergiants (Old)
• White and Brown Dwarfs (About to die)
Main Sequence Stars
• Hot and stable
• Changes hydrogen into helium
continuously.
• Stars stay here as long as hydrogen is
fused into helium. (about 5 billion years)
• Our sun is here! We are a yellow dwarf
Giants
• Red Giants
– Cools and expands following main sequence.
– Center shrinks and atmosphere expands
– Can be up to 10 times bigger than our sun
– Near end of life
Blue Giants
• Huge and Hot
• Very young stars…can expand into a blue
supergiant!
• Burns hydrogen to helium at a very fast
pace!
Red Supergiants
• Same as a red giant but…
• If star was huge to begin with, it will turn
into a red supergiant
• Can be up to 100 times bigger than the
sun.
Betelgeuse
White Dwarfs
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Mass of our sun or smaller
Virtually dead stars
Hot but only the center of the star is left
No hydrogen left to fuse into helium
Can shine for billions of years before
burning out completely
• Usually follows main sequence or red
giants.
Brown Dwarfs
• Extremely small dim stars
• Never fully got hot/bright enough following
their formation
• Usually can’t be seen with the naked eye
Birth of a New Star
•Stars are born in clusters and later move away from
each other as the universe continues to expand.
• The nebulas that stars are born in can be filled with
elements that were created in supernova explosions so
new stars being made can have many more elements
than those that were originally made 14 billion years ago.
Where are Stars Born?
• Astronomers believe that dense clouds of
gas located primarily in the spiral arms of
galaxies are the birthplace of stars.
• Initially, the gravitational energy of the
collapsing star is the source of its energy.
Once the star contracts enough that its
central core can burn hydrogen to
helium, (this is called Fusion) it becomes
a "main sequence" star.
Life Cycle of an Average Star
Star Facts
• Technically, the Sun is the closest star to the
Earth. It is approx. 8 light minutes away from
the earth. This means it would take light 8
minutes to travel the distance.
• The next closest star is Alpha Centauri and is
4.3 light YEARS away.
• Sirius is the brightest star in our night sky.
Life Cycle of Stars
Radiation from Space
• When you look at a star, the light that you see
left the star many years ago. Ex. It takes light
from the Sun 8.3 minutes to reach Earth.
• The light and other energy leaving a star are
forms of radiation. Radiation is energy that
is transmitted from one place to another by
electromagnetic waves.
• Because of the electric and magnetic radiation
it is called Electromagnetic Radiation.
• Electromagnetic waves carry energy through
empty space and through matter.
Electromagnetic Radiation
• Microwaves and visible light are just 2 types of
electromagnetic radiation.
• Other types include:
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Gamma rays
X rays
Ultraviolet waves
Infrared waves
Radiowaves
• The arrangement of electromagnetic radiation is called
the Electromagnetic Spectrum.
• Astronomers use the E. Spectrum to study
temperature and chemical composition of stars.
Visible Light
• Visible light is the light
that can be seen with
the unaided eye
• Other forms of
radiation can not be
seen with the unaided
eye (ex. Microwaves,
radio waves, etc)
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Millie is
amazed at all
the COOL
Things she
has been
learning
about
astronomy!
The Solar System
• The solar system
consists of our sun
and all the celestial
bodies (planets) that
revolve around it.
• The major members are
the Sun and the 8
planets + 1 dwarf planet.
• FACT: If the Sun were
hollow, more than 1
million Earth’s could fit
inside it.
Formation of the Solar System
• About 5 billion years ago, a dense area in the
center of our local cloud of rotating gases and
dust became our star, the Sun.
• This system of rotating gases was heated by the
friction of the rocks colliding into each other.
Lighter elements such as hydrogen and helium
were pushed out of the center and into the
edges of the disc, while heavier elements such
as dust and rocks were concentrated into the
center.
Planets
• There are 8 planets that revolve around
the sun. Planets change position in the
night sky verse the motionless stars.
• Planets do not give off their own light,
rather they reflect the light from the sun.
Solar System Formation
1.
2.
3.
4.
The young solar nebula begins to collapse
The solar nebula rotates flattens and becomes warmer near its center
Planetesimals begin to form within the swirling disk
As the largest planetesimals grow in size, their gravity attracts more gas and
dust.
5. Smaller planetesimals collide with the larger ones and planets begin to grow.
Balance of Pressure and
Gravity
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Gravity pulls matter together
Pressure pushes matter apart
Nebulas are less dense than air!
Gravity is pretty weak so particles won’t
naturally come together due to the
pressure.
• When the balance is upset (nearby
supernova, etc.) it can trigger star
formation.
Sun at the Center
• Polish astronomer Nicolaus Copernicus (14731543) proposed a heliocentric, or suncentered, model of the solar system.
• It wasn’t until a man named Johannes Kepler
(1571-1630), explained and described
planetary motion with mathematical laws that
the heliocentric model was accepted.
• In 1609, Galileo Galilei built a telescope and
became the first scientist to use this device to
study the night sky.
Planetary Motion
• Planets, asteroids, and comets move around the
Sun in a motion called Revolution. The path of
these objects is called their Orbit.
• The shape of the orbits for objects in the
solar system is elliptical.
• Each of the planets also spins on its axis. This
motion is called Rotation. It takes Earth 24 hrs
(1 Earth day) to rotate once on its axis.
Scientific Notation
• Scientific notation uses powers of ten to
write very large or very small numbers in
shorter form.
• For example: 1,200 is written as 1.2 x 103
• One light-year is about
9,500,000,000,000,000 meters. Since there
are 16 digits, in SN this number is written as
9.5 x 1015
Sun’s layers
Core
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Provides all the energy for the sun.
Where hydrogen is fused into helium
25% of the sun’s radius
27 million degrees Fahrenheit
Radiative Zone
• 55% of Sun’s radius
• Average temperature is 4.5 million
degrees Fahrenheit
• The heat from the core radiates through
this region.
Convective Zone
• Convection is how energy moves from the
inner part of the sun to the outer layers.
• Think boiling water…The heat of the water
from the bottom moves through the water
into the bubbles we see at the top where it
is cooler.
• 2 million degrees Fahrenheit
Photosphere
• Sun’s visible layer – heat from here is seen as
light on Earth – takes 8.3 minutes to reach Earth
• Sunspots appear on the outside
• Sunspots are cooler, darker spots on the
photosphere. They occur when activity slows
down in the convective zone. (Like some areas of
the water not boiling as much as others)
• 10,000 degrees Fahrenheit
• Sunspots are about 7,800 degrees F
Chromosphere
• Thin layer below the corona
• Has solar flares
• Solar flares are regions of extremely high
temperature and brightness that develop on the
sun’s surface.
• Caused by the sun’s magnetic fields and usually
associated with sunspots
• Can interrupt radio communications on Earth!
Corona
• Can only be seen during a total solar
eclipse
• 4 million degrees Fahrenheit –
astronomers have no idea why it has
heated up!
• The outer atmosphere of the sun
Planets in order from the Sun
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My
Very
Educated
Mother
Just
Served
Us
Nachos
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
The Planets
• The four inner planets are called terrestrial
planets. What does this mean?
• The four outer planets are called gas
giants? What does this mean?
• What is the asteroid belt and where is it
located?
The Solar System
Terrestrial Planets
• Order: Mercury, Venus, Earth, Mars
• Earth is the biggest
• All have a solid surface of rock and
landforms like mountains, craters and
valleys.
Gas Giants
• Much larger than the terrestrial planets.
• Composed mostly of gas rather than solid
rock
• Have elaborate ring systems and many
moons.
Mercury
• Has lots of craters left over from
solar system formation.
• Takes 88 days to revolve around
the Sun.
• Rotates VERY slow! One rotation
takes 58 Earth day!
• No atmosphere!
• Temperatures range from 800
degrees F to -280 degrees F due to
some parts of it never getting sun!
• Most dense next to Earth due to an
iron core.
Venus
• Brightest and hottest planet!
• About the same size as Earth.
• Covered with clouds of carbon
dioxide and sulfur.
• Takes 225 days to revolve around
the Sun.
• Takes 243 days to rotate once
so…It has a longer day than a year!
• Has mountains higher than Earth!
• Why can’t we live on Venus?
Mars
• Very thin atmosphere of mostly carbon
dioxide.
• Two moons: Deimos and Phobos.
• Dust storms can cover the planet for
months!
• Has large canyons, ice caps, volcanoes, and
sand dunes just like Earth.
• Second smallest and second brightest
planet.
• It appears reddish due to iron in its soil and
the atmosphere turning it a rusty color.
• Revolves around the sun every 687 days.
• Temperatures range from 70 degrees F to 225 degrees F.
• Mars rotates on its axis every 24 hours and
39 minutes…very similar to EARTH!
Jupiter
• Largest planet (11 times bigger than Earth)
• Takes 12 years to orbit the sun.
• Rotates in about 10 hours which is
ridiculously fast for how big it is!
• Has 63 moons and more keep being found!
• Jupiter has an extensive ring system which is
created by dust being kicked up as stuff hits
the moons of Jupiter. (They’ve found 4 rings
so far)
• Has a very stormy, windy atmosphere.
• It’s gravity (from being so big) is so large it
pulls tons of things into rotation around it so it
is nicknamed the vacuum cleaner.
• Average surface temperature is -185 degrees
F but it has a very hot core!
• The great red spot is a storm that has been
going on for over 300 years!
Saturn
• Second biggest planet.
• Has 62 moons found so far.
• Has 7 distinct rings around it made of
billions of particles of rocks, dust and ice.
• Extremely low density…like it could float
on water!
• Atmosphere made of mostly hydrogen and
helium.
• Has stormy weather similar to Jupiter.
• Twice as far away from the sun as Jupiter!!
• Rotates on its axis in about 10 ½ hours.
• 1 revolution around the sun takes about 30
years.
• Average temperature of -215 degrees F.
Uranus
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Average temperature is -357 degrees F
Has 27 moons.
Known as an Ice Giant.
Second lowest density next to Saturn.
Only planet with a very cool, rocky core.
Planet rotates on its side (possibly due to a large
object hitting it and causing the change in rotation)
1 rotation is about 17 hours
The weird tilt causes 42 years of sunlight and then 42
years of darkness.
A dim planet but with intricate rings.
Has strong winds and some clouds.
Scientists think it has a huge water ocean beneath the
clouds.
Atmosphere is hydrogen, helium and methane.
Blue/green color due to red light being absorbed by
methane.
Neptune
• Atmosphere is hydrogen, helium and methane
giving it a blue color just like Uranus. Has traces
of water and ammonia as well.
• Ball of gas and ice with a small rocky core.
• Fastest winds in the solar system and does
occasionally have spots like Jupiter which are
huge storms.
• Also has a ring system not as extensive as the
other gas giants.
• 1 revolution of the sun takes about 165 years.
• 1 rotation takes about 16 hours.
• Greater density than Uranus and Saturn.
• 13 moons found so far.
• Average temperature of -391 degrees F
Pluto
• It is not considered a planet anymore, but instead a
dwarf planet.
• Pluto’s atmosphere is made of 90% nitrogen and
10% other molecules. This is similar to Earth’s
atmosphere, which contains 80% nitrogen.
• Pluto’s temperature is measured in Kelvin, but if it
was converted to Fahrenheit it’s average
temperature would be -380°F.
• Pluto has four known moons with faint sights of
undiscovered moons. The four moons are Hydra, Nix,
Charon, and P4.
• It takes Pluto about six days for one rotation.
• Pluto’s revolution takes about 248 Earth years.
• Even though Pluto is not considered a planet it still
revolves around the sun and at certain times is closer
to the sun than Neptune.
http://astro.unl.edu/classaction/animations/coordsmotion/eclipticsimulator.html
http://www.mmscrusaders.com/newscirocks/tides/tideanim.htm
http://astro.unl.edu/classaction/animations/lunarcycles/lunar_phaser.html
Chemical Layers of the Earth
Chemical Layers of Earth
• 3 layers:
* Crust, Mantle, Core
* Layers determined by DENSITY!
* The layers most dense are at the center
and least dense are on the outside!
The Crust
• Thinnest layer
• 1% of Earth’s mass
• Continental crust – lighter, older and
thicker part of the crust which makes up
the continents.
• Oceanic crust – denser rock of the ocean
floor (more iron, calcium and magnesium)
The Mantle
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Thickest layer
67% of Earth’s mass
Uppermost part is solid
Middle acts like a thick liquid due to heat and
pressure
• Lowest part is even hotter but solid due to
tremendous pressure
• Magma (melted rock beneath Earth’s surface)
comes from the mantle
• Lava is magma that has reached the surface.
The Core
• 33% of Earth’s mass
• Mostly iron with a little nickle
Physical Layers of Earth
Physical Layers
• 6 layers:
• Crust
• Lithosphere, Asthenosphere,
Mesosphere (all part of mantle)
• Inner and Outer Core
Lithosphere
• Uppermost part of the mantle
• Made of tectonic plates – slow moving
chunks of rocks that fit like a giant jigsaw
puzzle and slide on the liquid part of the
mantle
• 12 large plates and several smaller ones
Asthenosphere
• Slow moving thick liquid of the mantle
• Flows due to convection currents
• Convection – heat from the core rises
causing the less heated magma to sink
and the hotter magma to rise to the top
• The convection currents keep repeating
and flowing shifting the tectonic plates.
Mesosphere
• In between the asthenosphere and the
outer core
• Largest layer of Earth
Inner & Outer Core
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Two parts: Inner and Outer
Outer – liquid
Inner – Solid due to enormous pressure
More than 6000 degrees Celcius and the
pressure is 4 million times that of our air
pressure!
Quick Quiz Question 1
• Which of the layers makes up most of
Earth’s mass?
A. Core
B. Mantle
C. Oceanic Crust
D. Continental Crust
Answer:
•The mantle makes
up most of Earth’s
mass!
Question 2
• In a cross section of the Earth, you
would label the center of the planet as
the:
A.
B.
C.
D.
Mantle
Crust
Inner Core
Outer Core
Question 2 Answer
• Inner core is the center
most part of the planet
and is solid due to the
pressure!
Question 3
• Which layer of the Earth consists
mostly of iron?
A.
B.
C.
D.
Core
Mantle
Oceanic Crust
Continental Crust
Question 3 Answer
•The core contains
mostly iron.
Question 4
• Which statement is true about Earth’s
tectonic plates?
A.
B.
C.
D.
They are floating on the core.
They are stable and do not move.
They are floating on the lithosphere.
They are floating on the
athenosphere.
Question 4 Answer
• They float on the
athenosphere which is the
thick liquid part of the
mantle. The lithosphere is
the layer of the tectonic
plates!
Question 5
• What is the only layer in the interior of
the Earth that is composed of liquid?
A.
B.
C.
D.
Crust
Mantle
Outer core
Inner core
Question 5 Answer
•The outer core is the
only layer that is made
of ALL liquid!