Download Celestial Bodies (Mike Stroppa) - Powerpoint

Early Astronomy
The Geocentric Model
Geo = Earth
Centric = Centred
Geocentric Model
• First described by Aristotle around 300 B.C.
• All celestial bodies seem to move across sky
from East-West
• Earth must be at the centre, with everything
moving around us
• Moon, Mercury, Venus, Sun, Mars, Jupiter,
Saturn – all fixed on circular spheres orbiting the
Earth.
• About 400 years later, new discoveries in
mathematics showed problems with the
Geocentric model
• Ptolemy (around 100 A.D.), updated the model,
adding “epicycles” to the orbits of the planets
• This helped to explain the retrograde motion of
some planets
• In total this model lasted for about 2000 years!
The Heliocentric Model
• Helio = Sun
Centric = Centred
•Copernicus (1500) devises a new model,
with the Sun at the centre
•Many new discoveries were being made at
this time to help prove this model
•Kepler (1600) improved the model by using
ellipses for the orbits instead of circles
Formation of the Universe
• Because it is believed that the Universe is
expanding, it must have started off as
something small
• The Big Bang occurred around 15-20 billion
years ago
• Formation of stars and galaxies shortly after
We are all Made of Stars
• An average star (like our Sun) lives for about 10
billion years
• Therefore, many stars have died out since the Big
Bang
• When a star explodes and dies, it is called a super
nova
These explosions supply the energy to make the
elements which everything is made up from
The Solar System
• The Sun, and anything orbiting the Sun
including the planets & their satellites,
comets, meteors, and asteroids.
• First existed as a solar nebula (a huge
cloud of gas and dust)
• Gravity pulls the nebula inward, and it begins
to rotate
• As the nebula rotates, it forms a flat disk
A Rotating Solar Nebula
• The material in the disk is what formed the
planets
• This is why all the planets are on the same
plane, and all orbit in a CCW direction
• The material in the centre is what formed
the Sun
Galaxy
• A large group of stars, gas, and dust
bound together by gravitational attractions
• The Milky Way is our galaxy
• There are approx 200 billion stars in the
Milky Way
• Scientist estimate that there are 100’s of
billions of galaxies
The Universe
• All space, along with all the matter and
radiation in space
• Anything and everything!
Solar Distances

Distances on Earth are measured in a
variety of units, depending on the distance
 If
really small:
 Size of a school:
 From WPG to VAN:
Micrometers
Meters
Kilometres
Units must change, because it would not
make sense to measure the distance from
Winnipeg to Vancouver in millimetres!
 If this distance was 1900 km, how many
mm?
 Almost 2 billion!
 1900 km = 1, 900, 000, 000 mm

Solar System Measurements
The distance from the Sun to the Earth is
155 million km
 This is too large of a number to use,
therefore when measuring distances in the
Solar System we use Astronomical
Units
 Each AU = 155 million km

Outside the Solar System
For any measurements outside the Solar
System, the AU is not very useful
 Closest star (Proxima Centauri) is 270 000
AU away
 Therefore we need to use a new unit

Light Year
A light Year is the distance light can travel
in one year
 Light moves at 3 X 108 m/s
 Earth is 155 million km away
 How long does it take light to reach the
Earth?


1) Change km to m
1.55 X 108 km = 1.55 X 1011 m

2) Divide this distance by the speed of
light
1.55 X 1011 m / 3 X 108 m/s = 516.75 s
The Third Rock From The Sun
A geologically active planet
- earthquakes, volcanoes
- erosion from wind & water
Large amounts of liquid water
- 70% of Earth’s surface
Unique atmosphere among the planets
- 80% nitrogen, 19% oxygen
• When the Earth first formed (4.6 billion
years ago) it was entirely molten
• Heavier elements sank towards the centre
• Lighter elements rose towards the surface
• Solid inner core (iron), molten outer core,
mantle, crust
Earth in Space
• The Earth revolves around the Sun once
every 365 days
• The Earth rotates on it’s axis once every
24 hours
• The axis is tilted 23.5 degrees
• Always pointed in the same direction
(North Star)
Reasons for the Seasons
• For half the year the Northern Hemisphere
is tilted toward the Sun (Summer!)
• For half the year the Northern Hemisphere
is tilted away from the Sun (Winter)
• This is the cause of the seasons!
Important Dates
•
•
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June 21: Summer Solstice
Arctic circle 24 hours daylight
March 21, Sept. 21: Spring & Fall Equinox
Everywhere receives 12 hours of day &
night
• Dec 21: Winter Solstice
• Arctic circle 24 hours of darkness
The Moon
• The most visible object in the night sky
• Can see surface features with the naked
eye
(Light grey/dark grey areas)
• Dark grey areas called “Maria”
• Latin for sea (People used to think these
areas were large bodies of water)
Characteristics
•
•
•
•
•
The Moon has many craters
Most small, but some up to 100 km
No water on the moon
No atmosphere
Surface covered with a fine powder and
rock fragments
How did the Moon Form?
• Early Earth struck by Mars sized object
• Tons of debris flown into space, orbits
around the Earth
• This debris later condensed together to
form the Moon
• Proof for this is in the composition of the
Moon
Moon Movements
• The Moon revolves around the Earth every
27 days
• The Moon revolves at the same rate it
rotates on its axis (1 moon day = 27 days!)
• Because of this, we never see the far side
of the Moon
• New moon to full moon: Waxing
• Full moon to new moon: Waning
The Sun
• The only star in our SS
• Makes up 99.9% of all the mass in the SS
• The source of almost all the energy on
Earth.
• Where does this energy come from?
Thermonuclear Reactions
• The Sun is made up of mostly Hydrogen
and Helium atoms
• It is so hot at the core that 2 hydrogen
atoms can fuse together to form helium
• This is called nuclear fusion
• Power plants use nuclear fision (opposite)
Sun Atmosphere
• The photosphere is the visible layer of
the Sun
• Not really a “surface”
• The chromosphere is visible only during
an eclipse
• The corona is the outermost region of the
Sun’s atmosphere
Sun Spots
• Regions of the photosphere that appear
dark because they are cooler than the
surrounding areas
• Can be about the size of the Earth
• Galileo first discovered sunspots
• He found they moved across the sun
• This proved the sun rotated on its axis
•
•
•
•
Sunspot cycle every 11 years
Last sunspot maximum: 2001
Last sunspot minimum: 1996
When there are many sunspots, Earth is
usually warmer
• When there are fewer sunspots, Earth is
usually colder
Solar Flares
• Huge eruptions from the photosphere
• Occur in large sunspot groups
• Radiation from these flares hit Earth,
interfere with radio communication, create
intense northern lights
Asteroids
• Left over pieces of rock and metal that did
not form planets
• Large asteroid belt between Mars and
Jupiter…………Destroyed planet?????
• Some up to 1000 km in diameter
• Paths crossing other asteroids, moons,
and planets
Comets
• AKA “dirty snowballs”
• Humans have been aware of comets for a
very long time, often considered bad
omens
• Discovered that comets reappear in cycles
• Halley’s Comet: Every 76 years.
• Last appearance in 1986, next in 2061
• Comets are made of two parts
• 1) Head (coma): Small dense nucleus,
surrounded by a large gas section
• 2) Tail: Made of fine particles of dust and
gas. Can be very long
• The tail can only be seen when the comet
approaches close enough to the Sun for it
to melt the iced gas
• The tail always points away from the Sun
• With each pass, the comet loses some of
its mass
Others……
• Meteoroid: Lumps of rock and metal, pulled
into Earth’s ATM
• Once a meteoroid enters the ATM it burns up
due to friction
• Meteor: A meteoroid that completely burns up
(shooting star)
• Meteor showers common several times a year
• Meteorite: An unburnt portion, Strikes the Earth
Meteor Showers
• On any given night you can expect to see a few
“shooting stars” each hour
• At certain times though, you can see many more
• Jan 4
110/h
• Aug 12
68/h
• Oct. 21
30/h
• Nov. 17
10/h
• Dec. 14
58/h
Stars
• If you ever looked up at the night sky, you
can see that the stars are not all the same
• They vary in Brightness
• They vary in colour
• They vary in size
Star Brightness
• Depends on the distance and size of the
star
• The Sun is so bright because it is so close
to us, but it is only an average star
• Luminosity: A measure of the total amount
of energy a star radiates per second
• Some stars are 30, 000 times more
luminous than the Sun
Star Colour
• Stars come in a variety of colours
• Scientists can tell the surface temperature
by the colour of the star
• Red stars are cooler (Surface T 3000 C)
• Blue stars are hotter (Surface T 20000 C)
• The Sun is a yellow star (6000 C)
Star Size
• Stars come in a variety of sizes
• Small stars are called dwarfs
• Large stars are called giants
• Our star is an average star
Dwarf Stars
• Low mass stars
• Slowly convert hydrogen into helium (over
100 billion years)
• May stay a dwarf all its life, our start as an
average star, and turn into a dwarf
• Red, white and Black dwarf stars
depending on age
Average Stars
• Consume their hydrogen in about 10
billion years
• (Our sun is about 5 billion years old)
• Once H is burned up, energy production
stops
• Core collapses due to gravity
• Increased T = increased pressure
• The outer layers of the star begin to
expand
• May become 100 times its original size
• Now called a red giant
• When our Sun reaches this stage it will
engulf Mercury, Venus, Earth and Mars!
• Eventually the outer gases are burnt off,
and all that is left is a super dense core
Massive Stars
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•
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Consume their hydrogen more rapidly
Millions of years, not billions
These stars become super giants
Life span shorter, but more energetic
Two fates once core collapses and
explodes (super nova)
• The star may turn into a neutron star, or a
black hole
Space Technology
• Telescope: a device used to magnify
distant objects
• Come in all sizes and shapes
• Refractor telescope uses glass lenses
• Reflector telescope uses mirror lenses
• The wider the telescope, the more light it
can process
Observatories
• A building designed and equipped with a
powerful telescope to observe the night
sky
• Best places: Arid regions, mountain tops
• Above cloud cover, away from light
pollution
• Hawaii & Chile are two of the best places
in the world, multiple observatories
Hubble Telescope
• What better place for a telescope than
outerspace?
• Launched in 1990
• Orbiting 600 km above the Earth
• Built by the European Space Agency
(ESA) and NASA
• Starting to become outdated
The Future
• The next generation telescope coming in
2009
• Called the James Web Space Telescope
Mir Space Station
• Launched in 1986 by the Russians
• Since then has had multiple upgrades
• Serves as a permanent site for
astronomers to conduct their research
• Shared by multiple countries